Model 3 Simplification based on cube & cube root Section-Wise Topic Notes With Detailed Explanation And Example Questions

MOST IMPORTANT quantitative aptitude - 4 EXERCISES

Top 10,000+ Aptitude Memory Based Exercises

The following question based on simplification topic of quantitative aptitude

Questions : The sum of the cubes of the numbers 22, –15 and –7 is equal to

(a) 0

(b) 6930

(c) 3

(d) 9630

The correct answers to the above question in:

Answer: (b)

Here, 22 - 15 - 7 = 0

We know that

$a^3 + b^3 + c^3$ = 3abc,

if a + b + c = 0

$(22)^3 + (–15)^3 + (–7)^3$

= 3 × 22 × (–15) (–7) = 6930

Practice simplification (Model 3 Simplification based on cube & cube root) Online Quiz

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Read more problems based on cubes and roots Based Quantitative Aptitude Questions and Answers

Question : 1

The square of a natural number subtracted from its cube is 48. The number is :

a) 4

b) 8

c) 5

d) 6

Answer: (a)

Let number be x

According to question,

$x^3 - x^2$ = 48 ⇒ ∴ x = 4

Question : 2

$√^3{0.000125}$ is equal to

a) 0.005

b) 0.5

c) 0.05

d) 0.15

Answer: (c)

$√^3{0.000125} = √^3{0.05 × 0.05 × 0.05}$

= 0.05

Question : 3

If cube root of 175616 is 56, then the value of $√^3{175.616} + √^3{0.175616} + √^3{0.000175616}$ is equal to :

a) 6.116

b) 0.168

c) 6.216

d) 62.16

Answer: (c)

Here, $√^3{175616}$ = 56

$√^3{175.616}$ = 5.6

$√^3{0.175616}$ = 0.56

and $√^3{0.000175616}$ = 0.056

Required sum

= 5.6 + 0.56 + 0.056 = 6.216

Question : 4

Which of the following is a perfect square as well as a cube? 343, 125, 81, or 64

a) 64

b) 81

c) 343

d) 125

Answer: (a)

343 = 7 × 7 × 7

125 = 5 × 5 × 5

81 = 3 × 3 × 3 × 3

64 = 8 × 8 = 4 × 4 × 4

We see that 343 and 125 are only perfect cubes of 7 and 5 respectively.

81 is only a perfect square of 9. 64 is a perfect square of 8 as well as a perfect cube of 4.

Question : 5

By what least number should 4320 be multiplied so as to obtain a number which is a perfect cube ?

a) 80

b) 40

c) 60

d) 50

Answer: (d)

4320 = 2 × 2 × 2 × 2 × 2 × 3 × 3 × 3 × 5

= $2^3 × 3^3 × 2^2 × 5$

Required number = 2 × 5 × 5 = 50

Question : 6

The sum of the squares of 2 numbers is 146 and the square root of one of them is $√5$. The cube of the other number is

a) 1441

b) 1111

c) 1331

d) 1221

Answer: (c)

First number = $(√5)^2 = 5$

Let the second number be x.

$x^2 + 5^2 = 146$

$x^2$ = 146 –25 = 121

$x = √{121} = 11$

Cube of 11 =1331

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