Volume and surface area - Quantitative Aptitude (MCQ) questions

1)   Volume of a sphere with radius r is obtained by multiplying its surface area by r and a constant. Find the value of constant:
- Published on 15 Jun 15

a. 3
b. 1/3
c. 4/3
d. 1
Answer  Explanation 

ANSWER: 1/3

Explanation:
Volume of a sphere: (4/3)* π*r3

Area of a sphere: 4πr2

=>It is mentioned that surface area when multiplied by r and a constant gives Volume and value of constant is to be found.

=> 4πr2*r*k= (4/3)* π*r3

=>k=1/3


2)   Radius of a circle is increased by 6%, determine the increase in area of the circle.
- Published on 15 Jun 15

a. 12%
b. 12.36%
c. 12.64%
d. 6%
Answer  Explanation 

ANSWER: 12.36%

Explanation:
Let old radius be 1r

As the radius has increased by 6%, the new radius = 1.06 r

New area = π (1.06r)2
=1.1236πr2

Increase: πr2 (1.1236) - πr2

=> 0.1236πr2 /πr2

=> 12.36%


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