RRB NTPC - Problems on Volumes

1.

If each edge of cube increased by 10%, the percentage increase in surface area is: 

   A.) 33.1%
   B.) 33%
   C.) 32.2
   D.) 32.3

Answer: Option 'A'

100 × (110)/100 × (110)/100 × (110)/100 => 1331/100 = 33.1%

2.

The radius of a cone is 10 m, height 21 m. The volume of the cone is:

   A.) 2220 m3
   B.) 2200 m2
   C.) 2200 m3
   D.) None of these

Answer: Option 'C'

1/3 πrh = 1/3 × 22/7 × 100 × 21 
= 2200 m3

3.

Three cubes of sides 5 m, 4 m, and 3 m are melted to form a new cube. Find the surface of the new cube? 

   A.) 216 Cm2
   B.) 256 Cm3
   C.) 216 Cm3
   D.) None of these

Answer: Option 'C'

Volume of the new cube = [ 53 + 43 + 33 ] Cm3
= 125 + 64 + 27 = 216 Cm3 => a3 = 216 Cm3

4.

The radius of hemi-sphere is 7 m. Find it's total surface area?

   A.) 452 m3
   B.) 462 m2
   C.) 462 m3
   D.) None of these

Answer: Option 'C'

otace area = 3πr2 sq.units 
= 3 × 22/7 × 7 × 7 
= 66 × 7 = 462 m3

5.

If the radius of sphere is doubled, then its volume is increased by: 

   A.) 100%
   B.) 200%
   C.) 700%
   D.) 800%

Answer: Option 'C'

radius = r. Original volume = 4/3 πr3
New radius = 2r New volume = 4/3 π(2r)3 = (32πr3)/3 
increase in volume = ( (32πr3)/3 × 3/(4πr3) × 100 ) % = 700%

Volumes in Mensuration Download Pdf