## Selina Concise Mathematics Class 8 ICSE Solutions Chapter 4 Cubes and Cube-Roots (Including use of tables for natural numbers)

**Selina Publishers Concise Mathematics Class 8 ICSE Solutions Chapter 4 Cubes and Cube-Roots (Including use of tables for natural numbers)**

### Cubes and Cube-Roots Exercise 4A – Selina Concise Mathematics Class 8 ICSE Solutions

Question 1.

Find the cube of :

(i) 7

(ii) 11

(iii) 16

(iv) 23

(v) 31

(vi) 42

(vii) 54

Solution:

Question 2.

Find which of the following are perfect cubes :

(i) 243

(ii) 588

(iii) 1331

(iv) 24000

(v) 1728

(vi) 1938

Solution:

Question 3.

Find the cubes of :

(i) 2.1

(ii) 0.4

(iii) 1.6

(iv) 2.5

(v) 0.12

(vi) 0.02

(vii) 0.8

Solution:

Question 4.

Find the cubes of :

(i) \(\frac { 3 }{ 7 }\)

(ii) \(\frac { 8 }{ 9 }\)

(iii) \(\frac { 10 }{ 13 }\)

(iv) \(1\frac { 2 }{ 7 }\)

(v) \(2\frac { 1 }{ 2 }\)

Solution:

Question 5.

Find the cubes of :

(i) -3

(ii) -7

(iii) -12

(iv) -18

(v) -25

(vi) -30

(vii) -50

Solution:

Question 6.

Which of the following are cubes of:

(i) an even number

(ii) an odd number

216, 729, 3375, 8000, 125, 343, 4096 and 9261.

Solution:

Question 7.

Find the least number by which 1323 must be multiplied so that the product is a perfect cube.

Solution:

Question 8.

Find the smallest number by which 8768 must be divided so that the quotient is a perfect cube.

Solution:

Question 9.

Find the smallest number by which 27783 be multiplied to get a perfect square number.

Solution:

Question 10.

With what least number must 8640 be divided so that the quotient is a perfect cube?

Solution:

Question 11.

Which is the smallest number that must be multiplied to 77175 to make it a perfect cube?

Solution:

### Cubes and Cube-Roots Exercise 4B – Selina Concise Mathematics Class 8 ICSE Solutions

Question 1.

Find the cube-roots of :

(i) 64

(ii) 343

(iii) 729

(iv) 1728

(v) 9261

(vi) 4096

(vii) 8000

(viii) 3375

Solution:

Question 2.

Find the cube-roots of :

(i) \(\frac { 27 }{ 64 }\)

(ii) \(\frac { 125 }{ 216 }\)

(iii) \(\frac { 343 }{ 512 }\)

(iv) 64 x 729

(v) 64 x 27

(vi) 729 x 8000

(vii) 3375 x 512

Solution:

Question 3.

Find the cube-roots of :

(i) -216

(ii) -512

(iii) -1331

(iv) \(\frac { -27 }{ 125 }\)

(v) \(\frac { -64 }{ 343 }\)

(vi) \(\frac { -512 }{ 343 }\)

(vii) -2197

(viii) -5832

(ix) -2744000

Solution:

Question 4.

Find the cube-roots of :

(i) 2.744

(ii) 9.261

(iii) 0.000027

(iv) -0.512

(v) -15.625

(vi) -125 x 1000

Solution:

Question 5.

Find the smallest number by which 26244 may be divided so that the quotient is a perfect cube.

Solution:

Question 6.

What is the least number by which 30375 should be multiplied to get a perfect cube?

Solution:

Question 7.

Find the cube-roots of :

(i) 700 x 2 x 49 x 5

(ii) -216 x 1728

(iii) -64 x -125

(iv) \(\frac { -27 }{ 343 }\)

(v) \(\frac { 729 }{ -1331 }\)

(vi) 250.047

(vii) -175616

Solution: