MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.4

Question 1.
Is it possible to have a triangle with the following sides?
(i) 2 cm, 3 cm, 5 cm
(ii) 3 cm, 6 cm, 7 cm
(iii) 6 cm, 3 cm, 2 cm
Solution:
In a triangle, the sum of the lengths of either two sides is always greater than the third side.
(i) Given that, the sides of the triangle are 2 cm, 3 cm, 5 cm.
It can be observed that,
(2 + 3) cm = 5 cm
However, 5 cm = 5 cm
Hence, this triangle is not possible.

(ii) Given that, the sides of the triangle are
3 cm, 6 cm, 7 cm.
Here, (3 + 6) cm = 9 cm > 7 cm
(6 + 7) cm = 13 cm > 3 cm
(3 + 7) cm = 10 cm > 6 cm
Hence, this triangle is possible.

(iii) Given that, the sides of the triangle are
6 cm, 3 cm, 2 cm.
Here, (6 + 3) cm = 9 cm > 2 cm
However, (3 + 2) cm = 5 cm < 6 cm Hence, this triangle is not possible.

Question 2.
Take any point 0 in the interior of a triangle PQR. Is
MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.4 1
(i) OP + OQ > PQ?
(ii) OQ + OR > QR?
(iii) OR + OP > RP?
Solution:
If O is a point in the interior of a given triangle, then three triangles ∆OPQ, ∆OQR and ∆ORP can be constructed. In a triangle, the sum of the lengths of either two sides is always greater than the third side.
(i) Yes, as OQR is a triangle with sides OR, OQ and QR.
MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.4 2
∴ OQ + OR> QR

(ii) Yes, as OQR is a triangle sides OR, OQ and QR.
∴ OQ + OR > QR

(iii) Yes, as A ORP is a triangle with sides OR, OP and PR.
∴ OR + OP > PR

Question 3.
AM is a median of a triangle ABC.
Is AB + BC + CA > 2AM?
(Consider the sides of ∆ABM and ∆AMC.)
MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.4 3
Solution:
In a triangle, the sum of the lengths of either two sides is always greater than the third side.
In ∆ABM,
AB + BM > AM …(i)
Similarly, in ∆ACM,
AC + CM > AM …(ii)
Adding (i) and (ii), we obtain
AB + BM + MC +AC > AM + AM
AB + BC + AC > 2AM
Yes, the given expression is true.

Question 4.
ABCD is a quadrilateral.
MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.4 4
Is AB + BC + CD + DA > AC + BD ?
Solution:
In a triangle, the sum of the lengths of either two sides is always greater than the third side.
In ∆ABC; AB + BC > CA …(i)
In ∆BCD; BC + CD > DB …(ii)
In ∆CDA; CD + DA > AC …(iii)
In ∆DAB; DA + AB > DB …(iv)
Adding (i), (ii), (iii) and (iv), we obtain
AB + BC + BC + CD + CD + DA + DA+ AB > AC + BD + AC + BD
⇒ 2AB + 2BC + 2CD + 2DA > 2AC + 2BD ⇒ 2{AB + BC + CD + DA) > 2(AC+BD)
⇒ (AB + BC + CD + DA) > (AC + BD)
Yes, the given expression is true.

Question 5.
ABCD is a quadrilateral.
MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.4 5
Is AB + BC + CD + DA < 2(AC + BD)?
Solution:
In a triangle, the sum of the lengths of either two sides is always greater than the third side.
Let diagonals AC and BD of the quadrilateral ABCD intersects at O.
MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.4 6
In ∆OAB, OA + OB > AB … (i)
In ∆OBC, OB + OC > BC … (ii)
In ∆OCD, OC + CD > CD … (iii)
In ∆ODA, OD + OA > DA … (iv)
OA + OB + OB + OC + OC + OD + OD + OA > AB + BC + CD + DA
⇒ 20A + 20B + 20C + 20D > AB + BC + CD + DA
⇒ 2(OA + OC) + 2(OB + OD) > AB + BC + CD + DA
⇒ 2(AC) + 2(BD) > AB + BC + CD + DA
⇒ 2(AC + BD) > AB + BC + CD + DA
Yes, the given expression is true.

Question 6.
The lengths of two sides of a triangle are 12 cm and 15 cm. Between what two measures should the length of the third side fall?
Solution:
In a triangle, the Sum of the lengths of either two side is always greater than the third side.
Lengths of two sides of a triangle are 12 cm and 15 cm.
Let the third side be x cm.
∴ x + 12 > 15 ⇒ x > 3
x + 15 > 12 ⇒ x > – 3 but side length never be negative.
and 12 + 15 > x ⇒ 27 > x
Hence, third side can measure between 3 and 27.

MP Board Class 7th Maths Solutions Chapter 6 The Triangles and Its Properties Ex 6.4

MP Board Class 7th Maths Solutions

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