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