Chapter 7: Cubes and Cube Roots 

Ex 7.1

1. Which of the following numbers are not perfect cubes? 

(i) 216 (ii) 128 (iii) 1000 (iv) 100 (v) 46656 

2. Find the smallest number by which each of the following numbers must be multiplied to obtain a perfect cube. 

(i) 243 (ii) 256 (iii) 72 (iv) 675 (v) 100 

3. Find the smallest number by which each of the following numbers must be divided to obtain a perfect cube.

 (i) 81 (ii) 128 (iii) 135 (iv) 192(v) 704 

4. Parikshit makes a cuboid of plasticine of sides 5 cm, 2 cm, 5 cm. How many suchcuboids will he need to form a cube?

                             Chapter 7. Cubes and Cube roots Ex 7.1 free pdf download

Ex 7.2 

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 

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.

3. You are told that 1,331 is a perfect cube. Can you guess without factorisationwhat is its cube root? Similarly, guess the Cube Roots of 4913, 

12167, 32768

                              Chapter 7 Ex 7.2 Cubes and cube roots free pdf download