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 : $√^3{(333)^3 + (333)^3 + (334)^3 - 3 × 333 × 333 × 334}$ is equal to

(a) 15

(b) 12

(c) 10

(d) 11

The correct answers to the above question in:

Answer: (c)

We know that

$a^3 + b^3 + c^3$ - 3abc

= (a+b+c)$(a^2+b^2+c^2$ - ab - bc - ca)

= $1/2 (a + b + c) [(a - b)^2 + (b - c)^2 + (c - a)^2 ]$

∴ $√^3{(333)^3 + (333)^3 + (334)^3 - 3 × 333 × 333 × 334}$

= $√^3{1/2 (333 + 333 + 334)[(333 - 333)^2 + (333 - 334)^2 + (334 - 333)^2]}$

= $√^3{1/2 × 1000 × 2} = √^3{1000}$

= $√^3{10 × 10 × 10}$ = 10

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 least number, by which 1944 must be multiplied so as to make the result a perfect cube, is

a) 13

b) 2

c) 6

d) 3

Answer: (d)

21944
2972
2486
3243
381
327
39
3

1944 = 2×2×2×3×3×3×3×3 = $2^3 × 3^3 × 3^2$

Clearly, 1944 should be multiplied by 3 to make the result a perfect cube.

Question : 2

$√^3{8}/√{16} ÷ √{100/49} × √^3{125}$ is equal to :

a) $4/7$

b) 7

c) $7/100$

d) 1$3/4$

Answer: (d)

On simplification,

Expression = $2/4 × 7/10 × 5$

= $7/4 = 1{3}/4$

Question : 3

$√^3{{72.9}/{0.4096}}$ is equal to :

a) 13.6

b) 0.5625

c) 182

d) 5.625

Answer: (d)

$√^3{{72.9}/{0.4096}} = √^3{{729000}/{4096}}$

= $√^3{(90)^3/(16)^3} = 90/16 = 45/8 = 5.625$

Question : 4

$√^3{4{12}/125}$ is equal to

a) 2.4

b) 1.4

c) 1.8

d) 1.6

Answer: (d)

Expression = $√^3{4{12}/125}$

= $√^3{512/125} = √^3{{8 × 8 × 8}/{5 × 5 × 5}} = 8/5$ =1.6

Question : 5

$(5.5)^3 - (4.5)^3$ is equal to :

a) 75.25

b) 1

c) 74.25

d) 75

Answer: (a)

$(5.5)^3 - (4.5)^3$

= $(5.5 - 4.5)^3$ + 3 × 5.5 × 4.5 (5.5 - 4.5)

= $(1)^3$ + 74.25(1)

= 1 + 74.25 = 75.25

Question : 6

The value of $(√{{4}^3 + {15}^2})^3$ is :

a) 3943

b) 4913

c) 4193

d) 4313

Answer: (b)

Expression = $(√{4^3 + {15}^2})^3$

= $(√{64 + 225})^3 = (√289)^3$

= $(17)^3$ = 4913

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