Problems on Areas : Aptitude Test

21.

If the radius of a circle decreased by 50% its area is decreased by:

   A.) 75%
   B.) 50%
   C.) 85%
   D.) 65%

Answer: Option 'A'

Original area = πr2 
New area = π(r/2)2 = (πr2)/4 
Reduction in area = [(πr2 - (πr2)/4]2 = (3πr2)/4 
Reduction percent = ((3πr2)/4 × 1/(πr2 × 100) % = 75%

22.

A rectangular room 14 m long, 12 m broad is surrounded by a varandah, 3 m wide. Find the area of the varandah? 

   A.) 190 m2
   B.) 170 m2
   C.) 180 m3
   D.) 180 m2

Answer: Option 'D'

Area of varandah = (l+b+2p)2p 
= (14 + 12 + 6 ) 6 
= 180 m2

23.

The area of the largest circle that can be drawn inside a square of side 28 Cm in length is:

   A.) 616 Cm3
   B.) 626 Cm2
   C.) 619 Cm2
   D.) 616 Cm2

Answer: Option 'D'

Radius of required circle = 14 Cm 
its area = 22/7 × 14 × 14 
44 × 14 = 616 Cm2

24.

Area of four walls of a room is 99 m2. The length and breadth of the room are 7.5 m and 3.5m respectively. The height of the room is:

   A.) 4.5 Cm
   B.) 5.5 m
   C.) 4.5 m
   D.) 5.5 Cm

Answer: Option 'C'

2(7.5+3.5)×h = 99 
2(11)h = 99 
22h = 99 
h = 99/22 = 9/2 = 4.5 m


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