Category: Class 7

MP Board Class 7th Maths Solutions Chapter 13 Exponents and Powers Ex 13.2

Question 1.
Using laws of exponents, simplify and write the answer in exponential form:
(i) 3² × 3⁴ × 3⁸
(ii) 6¹⁵ ÷ 6¹⁰
(iii) a³ × a²
(iv) 7^x × 7²
(v) (5²)³ 4 5³
(vi) 2⁵ × 5⁵
(vii) a⁴ × b⁴
(viii) (3⁴)³
(ix) (2²⁰ ÷ 2¹⁵) × 2³
(x) (8^t ÷ 8²)
Solution:
(i) 3² × 3⁴ × 3⁸ = (3)^{2 + 4 + 8} = 3¹⁴ [∵ a^m × aⁿ = a^m+n]
(ii) 6¹⁵ ÷ 6¹⁰ = (6)^{15 – 10} = 6⁵ [∵ a^m ÷ aⁿ = a^{m – n}]
(iii) a³ × a² = a^{3 + 2} = a⁵[∵ a^m × aⁿ = a^m+n]
(iv) 7^x × 7² = 7^{x + 2}[∵ a^m × aⁿ = a^m+n]
(v) (5²)³ ÷ 5³ = 5^{2 × 3} ÷ 5³ [∵ (a^m)ⁿ = a^mn]
= 5⁶ ÷ 5³ = 5^{(6 – 3)} [∵ a^m ÷ aⁿ = a^{m – n}]
= 5³
(vi) 2⁵ × 5⁵ = (2 × 5)⁵      [∵ a^m × b^m = (a × b)^m]
= 10⁵
(vii) a⁴ × b⁴ = (ab)⁴
(viii) (3⁴)³ = 3^{4 × 3} = 3¹²       [∵ (a^m)ⁿ = a^mn]
(ix) (2²⁰ ÷ 2¹⁵) × 2³ = (2^{20 – 15}) × 2³     [∵ a^m ÷ aⁿ = a^{m – n}]
= 2⁵ × 2³ = 2^{5 + 3} [∵ a^m × aⁿ = a^m+n]
(x) 8^t ÷ 8² = 8^{(t – 2)}    [∵ a^m ÷ aⁿ = a^{m – n}]

Question 2.
Simplify and express each of the following in exponential form:

Solution:

(ii) [(5²)³ × 5⁴] ÷ 5⁷
= [5^{2 × 3} × 5⁴] ÷ 5⁷ [∵ (a^m)ⁿ = a^mn]
= [5⁶ × 5⁴] ÷ 5⁷ [∵ a^m × aⁿ = a^{m + n}]
= [5^{6 + 4}] ÷ 5⁷
= 5¹⁰ ÷ 5⁷
= 5^{10 – 7} [∵ a^m ÷ aⁿ = a^{m – n}]
= 5³

(iii) 25⁴ ÷ 5³ = (5 × 5)⁴ ÷ 5³
= (5²)⁴ ÷ 5³ = 5^{2 × 4} ÷ 5³ [∵ (a^m)ⁿ = a^mn]
= 5⁸ ÷ 5³ = 5^{8 – 3} [∵ a^m ÷ aⁿ = a^{m – n}]
= 5⁵

(vi) 2⁰ + 3⁰ + 4⁰ = 1 + 1 + 1 = 3     [∵ a⁰ = 1]
(vii) 2⁰ × 3⁰ × 4⁰ = 1 × 1 × 1 = 1
(viii) (3⁰ + 2⁰) × 5⁰ = (1 + 1) × 1 = 2

Question 3.
Say true or false and justify your answer:
(i) 10 × 10¹¹ = 100¹¹
(ii) 2³ > 5²
(iii) 2³ × 3² = 6⁵
(iv) 3⁰ = (1000)⁰
Solution:
(i) L.H.S = 10 × 10¹¹
= 10^{1 + 11} = 10¹²
R.H.S = 100¹¹ = (10 × 10)¹¹ = (10⁰)¹¹ = 10^{2 × 11} = 10²²
⇒ L.H.S. ≠ R.H.S.
Hence, the given statement is false.

(ii) 2³ > 5²
L.H.S. = 2³ = 2 × 2 × 2 = 8
R.H.S. = 5³ = 5 × 5 = 25
⇒ L.H.S ≠ R.H.S
Hence, the given statement is false.

(iii) 2³ × 3² = 6⁵
L.H.S. = 2³ × 3² = 2 × 2 × 2 × 3 × 3 = 72
R.H.S. = 6⁵ = 6 × 6 × 6 × 6 × 6 = 7776
⇒ L.H.S. ≠ R.H.S.
Hence, the given statement is false.

(iv) 3⁰ = (1000)⁰
L.H.S. = 3⁰ = 1
R.H.S. = (1000)⁰ = 1
⇒ L.H.S. = R.H.S.
Hence, the given statement is true.

Question 4.
Express each of the following as a product of prime factors only in exponential form:
(i) 108 × 192
(ii) 270
(iii) 729 × 64
(iv) 768
Solution:
(i) 108 × 192
= (2 × 2 × 3 × 3 × 3) × (2 × 2 × 2 × 2 × 2 × 2 × 3)
= (2² × 3³) × (2⁶ × 3)
= 2²⁺⁶ × 3³⁺¹ = 2⁸ × 3⁴
(ii) 270 = 2 × 3 × 3 × 3 × 5 = 2 × 3³ × 5
(iii) 729 × 64 = (3 × 3 × 3 × 3 × 3 × 3) × (2 × 2 × 2 × 2 × 2 × 2) = 3⁶ × 2⁶
(iv) 768 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 3 = 2⁸ × 3

Question 5.
Simplify:

Solution:

MP Board Class 7th Maths Solutions

MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.3

Question 1.
Find the value of the unknown x in the following diagrams:


Solution:
The sum of all interior angles of a triangle is 180°. By using this property, these problems can be solved as follows :
(i) x + 50° + 60° = 180°
⇒ x +110° = 180°
⇒ x = 180° -110° = 70°

(ii) x + 90° + 30° = 180°
⇒ x + 120° = 180°
⇒ x = 180° – 120° = 60°

(iii) x + 30° + 110° = 180°
⇒ x + 140° = 180°
⇒ x = 180° – 140° = 40°

(iv) 50° + x + x = 180°
⇒ 2x = 180° – 50° = 130°

(v) x + x + x = 180°
⇒ 3x = 180°

(vi) x + 2x + 90° = 180°
⇒ 3x = 180° – 90° = 90° = 90°

Question 2.
Find the values of the unknowns x and y in the following diagrams:

Solution:
(i) y + 120° = 180° (Linear pair)
⇒ y = 180° – 120° = 60°
Now, x + y + 50° = 180°
(Angle sum property)
⇒ x + 60° + 50° = 180° x = 180° – 60° – 50° = 70°

(ii) y = 80° (Vertically opposite angles)
Now, y + x + 50° = 180°
(Angle sum property)
⇒ 80° + x + 50° = 180°
⇒ x = 180° – 80°- 50° = 50°

(iii) y + 50° + 60° = 180°
(Angle sum property)
⇒ y = 180° – 60° – 50° = 70°
Now, x + y = 180° (Linear pair)
⇒ x = 180° – y = 180° – 70° = 110°

(iv) x = 60° (Vertically opposite angles)
Now, 30° + x + y = 180°
(Angle sum property)
⇒ 30° + 60° + y = 180° y = 180° – 30° – 60° = 90°

(v) y = 90° (Vertically opposite angles)
Now, x + x + y = 180°
(Angle sum property)
⇒ 2x + 90° = 180°
⇒ 2x = 180° – 90° = 90°

(vi) y = x (Vertically opposite angles)
a = x (Vertically opposite angles)
b = x (Vertically opposite angles)
Now, a + b + y = 180°
(Angle sum property)
⇒ x + x + x= 180°
⇒ 3x = 180°


Hence, y = x = 60°

MP Board Class 7th Maths Solutions

MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.2

Question 1.
Find the value of the unknown exterior angle x in the following diagrams:


Solution:
(i) x = 50° + 70° (Exterior angle property) = 120°
(ii) x = 65° + 45° (Exterior angle property)
= 110°
(iii) x = 40° + 30° (Exterior angle property)
= 70°
(iv) x = 60° + 60° (Exterior angle property)
= 120°
(v) x = 50° + 50° (Exterior angle property)
= 100°
(vi) x = 30° + 60° (Exterior angle property)
= 90°

Question 2.
Find the value of the unknown interior angle x in the following figures:


Solution:
(i) x + 50° = 115°
(Exterior angle property)
⇒ x = 115° – 50° = 65°
(ii) 70° + x = 100° (Exterior angle property) ⇒ x = 100° – 70° = 30°
(iii) x + 90° = 125° (Exterior angle property) ⇒ x = 125° – 90° = 35°
(iv) x + 60° = 120° (Exterior angle property) ⇒ x = 120° – 60° = 60°
(v) x + 30° = 80° (Exterior angle property) ⇒ x = 80° – 30° = 50°
(vi) x + 35° = 75° (Exterior angle property) ⇒ x = 75° – 35° = 40°

MP Board Class 7th Maths Solutions

MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.1

Question 1.
In ∆PQR, D is the mid-point of \(\overline{Q R}\).
\(\overline{P M}\) is ___.
PD is ___.
Is QM = MR?

Solution:
(i) PM is an altitude
(ii) PD is a median
(iii) No, QM ≠ MR.

Question 2.
Draw rough sketches for the following:
(a) In ∆ABC, BE is a median.
(b) In ∆PQR, PQ and PR are altitudes of the triangle.
(c) In ∆XYZ, YL is an altitude in the exterior of the triangle.
Solution:

Question 3.
Verify by drawing a diagram, if the median and altitude of an isosceles triangle can be same.
Solution:

Draw a line segment AD perpendicular to BC. It can be observed that the length of BD and DC is also same. Therefore, AD is also a median of this triangle.

MP Board Class 7th Maths Solutions

MP Board Class 7th Social Science Solutions Chapter 19 Weather and Climate

MP Board Class 7th Social Science Chapter 19 Text Book Questions

Fill in the blanks:

1.  Weather affects a area.
2. Almost similar atmospheric condition is called
3. elements are found in climate and weather.

Answer:

1. small
2. season
3. Six.

MP Board Class 7th Social Science Chapter 19 Short Answer Type Questions

Question 1.
What is weather? What is difference between weather and season.
Answer:
Weather is the condition of atmosphere at a given place for a short-period with regard to its temperature, rainfall, pressure, humidity and direction of wind. Weather can change-many times in a day.
Difference between weather ans season.
Answer:
Weather:

• Weather Is a short duration atmospheric condition.
• Weather represents the atmospheric condition of a small area.
• Weather can change many time In a day.

Season:

• Season Is a long duration atmospheric condition.
• Season represents the atmospheric condition of a Large area.
• Season does not change for a long period.

Question 2.
To analyse the climate of an area how many years average data is taken?
Answer:
To analyse die climate of an area we have to take the average data of the weather conditions of the place of at least 30 years.

Question 3.
Which are the factors affecting the climate of a place?
Answer:
The factors affecting the climate of a place are:

1. The latitudinal position of a place.
2. Height from sea level.
3. The distribution of land and water.
4. Distance from sea.
5. Direction of wind.
6. Air pressure belts.
7. Situation of mountains.
8. Nature of land.
9. Ocean currents.

MP Board Class 7th Social Science Chapter 19 Long Answer Type Questions

Question 1.
Differentiate between weather and climate.
Answer:
The following are the difference of weather and climate.
Weather:

• Weather is a short durat – tion atmospheric condition.
• Weather represents the atmospheric condition of dsmall area.
• The weather can change many times in a day.
• In the weather of one sea – son any one element is prominent.

Climate

• Climate is a long duration atmospheric condition.
• Climate represents the wide area of atmo – spheric condition.
• The climate does not change for long periods.
• In one type of climate one or many seasons we there.

MP Board Class 7th Social Science Solutions

MP Board Class 7th Maths Solutions Chapter 13 Exponents and Powers Ex 13.1

Question 1.
Find the value of
(i) 2⁶
(ii) 9³
(iii) 11²
(iv) 5⁴
Solution:
(i) 2⁶ = 2 × 2 × 2 × 2 × 2 × 2 = 64
(ii) 9³ = 9 × 9 × 9 = 729
(iii) 11² = 11 × 11= 121
(iv) 5⁴ = 5 × 5 × 5 × 5 = 625

Question 2.
Express the following in exponential form:
(i) 6 × 6 × 6 × 6
(ii) t × t
(iii) b × b × b × b
(iv) 5 × 5 × 7 × 7 × 7
(v) 2 × 2 × a × a
(vi) a × a × a × c × c × c × c × d
Solution:
(i) 6 × 6 × 6 × 6 = 6⁴
(ii) t × t = t²
(iii) b × b × b × b = b⁴
(iv) 5 × 5 × 7 × 7 × 7 = 5² × 7³
(v) 2 × 2 × a × a = 2² × a²
(vi) a × a × a × c × c × c × c × d = a³ × c⁴ × d

Question 3.
Express each of the following numbers using exponential notation:
(i) 512
(ii) 343
(iii) 729
(iv) 3125
Solution:
(i) 512 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 = 2⁹
(ii) 343 = 7 × 7 × 7 = 7³
(iii) 729 = 3 × 3 × 3 × 3 × 3 × 3 = 3⁶
(iv) 3125 = 5 × 5 × 5 × 5 × 5 = 5⁵

Question 4.
Identify the greater number, wherever possible, in each of the following?
(i) 4³ or 3⁴
(ii) 5³ or 3⁵
(iii) 2⁵ or 8²
(iv) 100² or 2¹⁰⁰
(v) 2¹⁰ or 100²
Solution:
(i) 4³ = 4 × 4 × 4 = 64 and 3⁴ = 3 × 3 × 3 × 3 = 81
As 81 > 64, therefore 3⁴ > 4³

(ii) 5³ = 5 × 5 × 5 = 125,
3⁵ = 3 × 3 × 3 × 3 × 3 = 243
As 243 > 125, therefore, 3⁵ > 5³

(iii) 2⁸ = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 = 256,
8² = 8 × 8 = 64
As 256 > 64, therefore, 2⁸ > 8²

(iv) 2¹⁰⁰ = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 = 1024
⇒ 2¹⁰⁰ = (2¹⁰)¹⁰ = 1024 × 1024 × 1024 × 1024 × 1024 × 1024 ×1024 ×1024 × 1024 × 1024 = (1024)¹⁰
and 100² = 100 × 100 = 10000
As (1024)¹⁰ > 10000, therefore 2¹⁰⁰ > 100²

(v) 2¹⁰ = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 = 1024
and 10² = 10 × 10 = 100
As 1024 > 100, therefore 2¹⁰ > 10²

Question 5.
Express each of the following as product of powers of their prime factors:
(i) 648
(ii) 405
(iii) 540
(iv) 3600
Solution:
(i) 648 = 2 × 2 × 2 × 3 × 3 × 3 × 3 = 2³ × 3⁴
(ii) 405 = 3 × 3 × 3 × 3 × 5 = 3⁴ ×5
(iii) 540 = 2 × 2 × 3 × 3 × 3 × 5 = 2² × 3³ × 5
(iv) 3600 = 2 × 2 × 2 × 2 × 3 × 3 × 5 × 5 = 2⁴ × 3² × 5²

Question 6.
Simplify:
(i) 2 × 10³
(ii) 7² × 2²
(iii) 2³ × 5
(iv) 3 × 4⁴
(v) 0 × 10²
(vi) 5² × 3³
(vii) 2⁴ × 3²
(viii) 32 × 104
Solution:
(i) 2 × 10³ = 2 × 10 × 10 × 10 = 2 × 1000 = 2000
(ii) 7² × 2² = 7 × 7 × 2 × 2 = 49 × 4 = 196
(iii) 2³ × 5 = 2 × 2 × 2 × 5 = 8 × 5 = 40
(iv) 3 × 4⁴ = 3 × 4 × 4 × 4 × 4 = 3 × 256 = 768
(v) 0 × 10² = 0 × 10 × 10 = 0
(vi) 5² × 3³ = 5 × 5 × 3 × 3 × 3 = 25 × 27 = 675
(vii) 2⁴ × 3⁴ = 2 × 2 × 2 × 2 × 3 × 3 = 16 × 9 = 144
(viii) 3² × 10⁴ = 3 × 3 × 10 × 10 × 10 × 10 = 9 × 10000 = 90000

Question 7.
Simplify:
(i) (-4)³
(ii) (-3) × (-2)³
(iii) (-3)² × (-5)²
(iv) (-2)³ × (-10)³
Solution:
(i) (-4)³ = (-4) × (-4) × (-4) = -64
(ii) (-3) × (-2)³ = (-3) × (-2) × (-2) × (-2) = (-3) × (-8) = 24
(iii) (-3)² × (-5)² = (-3) × (-3) × (-5) × (-5) = 9 × 25 = 225
(iv) (-2)³ × (-10)³ = (-2) × (-2) × (-2) × (-10) × (-10) × (-10) = (-8) × (-1000) = 8000

Question 8.
Compare the following numbers:
(i) 2.7 × 10¹²; 1.5 × 10⁸
(ii) 4 × 10¹⁴; 3 × 10¹⁷
Solution:
(i) 2.7 × 10¹²; 1.5 × 10⁸
Since, 10¹² > 10⁸
∴ 2.7 × 10¹² > 1.5 × 10⁸
(ii) 4 × 10¹⁴; 3 × 10¹⁷
Since, 10¹⁴ < 10¹⁷
∴ 4 × 10¹⁴ < 3 × 10¹⁷

MP Board Class 7th Maths Solutions

MP Board Class 7th Maths Solutions Chapter 5 Lines and Angles Ex 5.2

Question 1.
State the property that is used in each of the following statements?
(i) If a||b, then ∠1 = ∠5.
(ii) If ∠4 = ∠6, then a||b.
(iii) If ∠4 + ∠5 = 180°,then a||b.

Solution:
(i) Corresponding angles property
(ii) Alternate interior angles property
(iii) Interior angles on the same side of the transversal are supplementary.

Question 2.
In the adjoining figure, identify

(i) the pairs of corresponding angles.
(ii) the pairs of alternate interior angles.
(iii) the pairs of interior angles on the same side of the transversal.
(iv) the vertically opposite angles.
Solution:
(i) ∠1 and ∠5; ∠2 and ∠6;
∠3 and ∠7; ∠4 and ∠8
(ii) ∠2 and ∠8; ∠3 and ∠5
(iii) ∠2 and ∠5; ∠3 and ∠8
(iv) ∠1 and ∠3; ∠2 and ∠4;
∠5 and ∠7; ∠6 and ∠8

Question 3.
In the adjoining figure, p||q. Find the unknown angles.

Solution:
∠d = 125° (Corresponding angles)
∠e = 180° – 125° = 55° (Linear pair)
∠f = ∠e = 55° (Vertically opposite angles)
∠c = ∠f = 55° (Corresponding angles)
∠a = ∠e – 55° (Corresponding angles)
∠b = ∠d = 125° (Vertically opposite angles)

Question 4.
Find the value of x in each of the following figures l ||m

Solution:
(i) We have,

y = 110° (Corresponding angles)
x + y = 180° (Linear pair)
⇒ x = 180° -110° = 70°

(ii) x = 100° (Corresponding angles)

Question 5.
In the given figure, the arms of two angles are parallel. If ∠ABC = 70°, then find
(i) ∠DGC
(ii) ∠DEF

Solution:
(i) Consider that AB||DG and a transversal line BC is intersecting them.
∴ ∠DGC = ∠ABC (Corresponding angles)
⇒ ∠DGC = 70°

(ii) Consider that BC 11 EF and a transversal line DE is intersecting them.
∴ ∠DEF = ∠DGC (Corresponding angles)
⇒ ∠DEF = 70°

Question 6.
In the given figures below, decide whether l is parallel to m.


Solution:
(i) Consider two lines l and m and a transversal line n which is intersecting them. Sum of the interior angles on the same side of transversal = 126° + 44° = 170°.
As the sum of interior angles on the same side of the transversal is not 180°, therefore, 1 is not parallel to m.

(ii) We have,

x + 75° = 180°(Linear pair on line l)
⇒ x = 180° – 75° = 105°
For l and m to be parallel to each other, corresponding angles (∠ABC and x) should be equal. However, here their measures are 75° and 105°. Hence, the lines l and m are not parallel to each other.

(iii) We have,

x + 123° = 180° (Linear pair on line m)
⇒ x = 180° – 123° = 57°
For l and m to be parallel to each other, corresponding angles (∠ABC and x) should be equal. However their measures are equal to 57°. Hence, l||m.

(iv) We have,

98° + x = 180°(Linear pair on line l)
⇒ x = 180° – 98° = 82°
For l and m to be parallel to each other, corresponding angles (∠ABC and x) should be equal. However, their measures are 72° and 82°. Hence, the lines l and m are not parallel to each other.

MP Board Class 7th Maths Solutions

MP Board Class 7th Maths Solutions Chapter 14 Symmetry Ex 14.3

Question 1.
Name any two figures have both line symmetry and rotational symmetry.
Solution:
An equilateral triangle and regular hexagon have both line symmetry and rotational symmetry.

Question 2.
Draw, wherever possible, a rough sketch of
(i) a triangle with both line and rotational symmetries of order more than 1.
(ii) a triangle with only line symmetry and no rotational symmetry of order more than 1.
(iii) a quadrilateral with a rotational symmetry of order more than 1 but not a line symmetry.
(iv) a quadrilateral with line symmetry but not a rotational symmetry of order more than 1.
Solution:
(i) An equilateral triangle has 3 lines of symmetry and rotational symmetry of order 3.

(ii) An isosceles triangle has only 1 line of symmetry and no rotational symmetry of order more than 1.

(iii) A parallelogram is a quadrilateral which has no line symmetry but a rotational symmetry of order 2.

(iv) A kite is a quadrilateral which has only 1 line of symmetry and no rotational- symmetry of order more than 1.

Question 3.
If a figure has two or more lines of symmetry, should it have rotational symmetry of order more than 1 ?
Solution:
Yes, if a figure has two or more lines of symmetry, then it will definitely have its rotational symmetry of order more than 1.

Question 4.
Fill in the blanks:

Solution:
The given table can be completed as follows:

Question 5.
Name the quadrilaterals which have both line and rotational symmetry of order more than 1.
Solution:
Square, rectangle, and rhombus are the quadrilaterals which have both line and rotational symmetry of order more than 1. A square has 4 lines of symmetry and rotational symmetry of order 4. A rectangle has 2 lines of symmetry and rotational symmetry of order 2. A rhombus has 2 lines of symmetry and rotational symmetry of order 2.

Question 6.
After rotating by 60° about a centre, a figure looks exactly the same as its original position. At what other angles will this happen for the figure?
Solution:
It can be observed that if a figure looks symmetrical on rotating by 60°, then it will also look symmetrical on rotating by 120°, 180°, 240°, 300°, 360° i.e., further multiples of 60°.

Question 7.
Can we have a rotational symmetry of order more than 1 whose angle of rotation is
(i) 45°?
(ii) 17°?
Solution:
It can be observed that if the angle of rotation of a figure is a factor of 360°, then it will have a rotational symmetry of order more than 1.
(i) It can be checked that 45° is a factor of 360°. Therefore, the figure having its angle of rotation as 45° will have its rotational symmetry of order more than 1.
(ii) 17° is not a factor of 360°. Therefore, the figure having its angle of rotation as 17° will not be having its rotational symmetry of order more than 1.

MP Board Class 7th Maths Solutions

MP Board Class 7th Maths Solutions Chapter 5 Lines and Angles Ex 5.1

Question 1.
Find the complement of eachof the following angles:

Solution:
The sum of the measures of complementary angles is 90°.
(i) Complement of 20° = 90°- 20° = 70°
(ii) Complement of 63° = 90° – 63° = 27°
(iii) Complement of 57° = 90° – 57° = 33°

Question 2.
Find the supplement of each of the following angles:

Solution:
The sum of measures of supplementary angles is 180°.
(i) Supplement of 105° = 180° – 105° = 75°
(ii) Supplement of 87° = 180° – 87° = 93°
(iii) Supplement of 154° = 180° – 154° = 26°

Question 3.
Identify which of the following pairs of angles are complementary and which are supplementary.
(i) 65°, 115°
(ii) 63°, 27°
(iii) 112°, 68°
(iv) 130°, 50°
(v) 45°, 45°
(vi) 80°, 10°
Solution:
The sum of the measures of complementary angles is 90° and that of supplementary angles is 180°.
(i) Sum of the measures of angles = 65° +115° = 180°
∴ These angles are supplementary angles.
(ii) Sum of the measures of angles = 63° + 27° = 90°
∴ These angles are complementary angles.
(iii) Sum of the measures of angles = 112° + 68° = 180°
∴ These angles are supplementary angles.
(iv) Sum of the measures of angles = 130° + 50° = 180°
∴ These angles are supplementary angles.
(v) Sum of the measures of angles = 45° + 45° = 90°
∴ These angles are complementary angles.
(vi) Sum of the measures of angles = 80°+ 10° =90°
∴ These angles are complementary angles.

Question 4.
Find the angle which is equal to its complement.
Solution:
Let the angle be x.
Complement of this angle is also x.
∵ The sum of the measures of a pair of complementary angles is 90°.
∴ x + x = 90° ⇒ 2x = 90°

Question 5.
Find the angle which is equal to its supplement.
Solution:
Let the angle be x.
Supplement of this angle is also x.
∵ The sum of the measures of a pair of supplementary angles is 180°.
∴ x + x = 180°
⇒ 2x = 180° ⇒ x = 90°

Question 6.
In the given figure, ∠1 and ∠2 are supplementary angles. If ∠1 is decreased, what changes should take place in ∠2 so that both the angles still remain supplementary.

Solution:
∠1 and ∠2 are supplementary angles.
If ∠1 is decreased, then ∠2 should be increased by the same measure so that the given pair of angles remains supplementary.

Question 7.
Can two angles be supplementary if both of them are:
(i) acute?
(ii) obtuse?
(iii) right?
Solution:
(i) No. Acute angle is always less than 90°. It can be observed that two angles, even of 89°, cannot add up to 180°. Therefore, two acute angles cannot form a supplementary.
(ii) No. Obtuse angle is always greater than 90°. It can be observed that two angles, even of 91°, will always add up to more than 180°. Therefore, two obtuse angles cannot form a supplementary.
(iii) Yes. Right angles are of 90° and 90° + 90° = 180°.
Therefore, two right angles form a supplementary angle together.

Question 8.
An angle is greater than 45°. Is its complementary angle greater than 45° or equal to 45° or less than 45°?
Solution:
Let A and B are two angles making a complementary angle pair and A is greater than 45°.
A + B = 90°
⇒ B = 90° – A
Therefore, B will be less than 45°.

Question 9.
In the adjoining figure:

(i) Is ∠1 adjacent to ∠2?
(ii) Is ∠AOC adjacent to ∠AOE?
(iii) Do ∠COE and ∠EOD form a linear pair?
(iv) Are ∠BOD and ∠DOA supplementary?
(v) Is ∠1 vertically opposite to ∠4?
(vi) What is the vertically opposite angle of ∠5?
Solution:
(i) Yes. Since, ∠1 and ∠2 have a common vertex O and a common arm OC. Also, their non-common arms OA and OE are on the opposite side of the common arm.
(ii) No. ∠AOC and ∠AOE have a common vertex O and also a common arm OA. But, their non-common arms OC and OE are on the same side of the common arm. Therefore, they are not adjacent to each other.
(iii) Yes. Since, ∠COE and ∠EOD have a common vertex O and a common arm OE. Also, their non-common arms, OC and OD, are opposite rays.
(iv) Yes. Since, ∠BOD and ∠DOA have a common vertex O and their non-common arms are opposite to each other.
(v) Yes. Since, ∠1 and ∠4 are formed due to the intersection of two straight lines, AB and CD.
(vi) ∠COB is the vertically opposite angle of ∠5 as they are formed due to the intersection of two straight lines, AB and CD.

Question 10.
Indicate which pairs of angles are:
(i) Vertically opposite angles.
(ii) Linear pairs.

Solution:
(i) ∠1 and ∠4, ∠5 and ∠2 + ∠3 are vertically opposite angles as they are formed due to the intersection of two straight lines.
(ii) ∠1 and ∠5, ∠5 and ∠4 are forming linear pairs as they have a common vertex and also, have non-common arms opposite to each other.

Question 11.
In the following figure, is ∠1 adjacent to ∠2? Give reasons.

Solution:
∠1 and ∠2 are not adjacent angles because their vertex is not common.

Question 12.
Find the values of the angles x, y and z in each of the following:

Solution:
(i) Since, x and 55° are vertically opposite angles,
x = 55° .
x + y = 180° (Linear pair)
⇒ 55° + y = 180°
⇒ y = 180° – 55° = 125°
y = z (Vertically opposite angles)
∴ z = 125°

(ii) z = 40° (Vertically opposite angles)
y + z = 180° (Linear pair)
⇒ y = 180° – 40° = 140°
∵ 40° + x + 25° = 180°
(Angles on a straight line)
⇒ 65° + x = 180°
⇒ x = 180° – 65° = 115°

Question 13.
Fill in the blanks:
(i) If two angles are complementary, then the sum of their measures is ___ .
(ii) If two angles are supplementary, then the sum of their measures is ___.
(iii) Two angles forming a linear pair are ___.
(iv) If two adjacent angles. are supplementary, they form a ___.
(v) If two lines intersect at a point, then the vertically opposite angles are always ___.
(vi) If two lines intersect at a point, and if one pair of vertically opposite angles are acute angles, then the other pair of vertically opposite angles are ___.
solution:
(i) 90°
(ii) 180°
(iii) supplementary
(iv) linear pair
(v) equal
(vi) obtuse angles

Question 14.
In the adjoining figure, name the following pairs of angles.

(i) Obtuse vertically opposite angles
(ii) Adjacent complementary angles
(iii) Equal supplementary angles
(iv) Unequal supplementary angles
(v) Adjacent angles that do not form a linear pair
Solution:
(i) ∠AOD, ∠BOC
(ii) ∠EOA, ∠AOB
(iii ) ∠EOB, ∠EOD
(iv) ∠EOA, ∠EOC
(v) ∠AOB and ∠AOE; ∠AOE and ∠EOD; ∠EOD and ∠DOC

MP Board Class 7th Maths Solutions

MP Board Class 7th Maths Solutions Chapter 14 Symmetry Ex 14.2

Question 1.
Which of the following figures have rotational symmetry of order more than 1 :

Solution:
(a) The given figure has its rotational symmetry of order 4.

(b) The given figure has its rotational symmetry of order 3.

(c) The given figure has its rotational symmetry of order 1.

(d) The given figure has its rotational symmetry of order 2.

(e) The given figure has its rotational symmetry of order 3.

(f) The given figure has its rotational symmetry of order 4.

Hence, figures (a), (b), (d), (e) and (f) have rotational symmetry of order more than 1.

Question 2.
Give the order of rotational symmetry for each figure:

Solution:
(a) The given figure has rotational symmetry of order 1.

(b) The given figure has rotational symmetry of order 2.

(c) The given figure has rotational symmetry of order 3.

(d) The given figure has rotational symmetry of order 4.

(e) The given figure has rotational symmetry of order 4.

(f) The given figure has rotational symmetry of order 5.

(g) The given figure has rotational symmetry of order 6.

(h) The given figure has rotational symmetry of order 3.

MP Board Class 7th Maths Solutions