Class 8, Maths, Chapter 7, Exercise 7.2, Solutions

Q.1. Find the cube root of each of the following numbers by prime factorisation method.

(i) 64

(ii) 512

(iii) 10648

(iv) 27000

(v) 15625

(vi) 13824

(vii) 110592

(viii) 46656

(ix) 175616

(x) 91125

Q.2. State true or false.

(i) Cube of any odd number is even.

(ii) A perfect cube does not end with two zeros.

(iii) If square of a number ends with 5, then its cube ends with 25.

(iv) There is no perfect cube which ends with 8.

(v) The cube of a two digit number may be a three digit number.

(vi) The cube of a two digit number may have seven or more digits.

(vii) The cube of a single digit number may be a single digit number.

Ans:

(i) False

(ii) True

(iii) True

(iv) False

(v) False

(vi) False

(vii) True

Q.3. You are told that 1,331 is a perfect cube. Can you guess without factorisation what is its cube root? Similarly, guess the cube roots of 4913, 12167, 32768.

Ans: 1^{st} pair = 331

Unit digit =1

Cube root digit =1

2^{nd} pair = 1

Cube root tens digit = 1

Therefore, answer is 11.

NCERT Solutions For Class 8 Maths Chapter 7, Cubes and Cube Roots (All Exercises)