Q31
The height of a solid cylinder in 30 cm and the diameter of its base is 10 cm. Two identical conical holes each of radius 5 cm and height 12 cm are drilled out. What is the surface area (in cm2) of the remaining solid?
A.
430π
AnswerB.
230π
C.
330π
D.
120π
Answer: Option A
Solution
Answer: Option A
Solution:

L.S.A. of cylinder = 2πrh
= 2 × × 5 × 30
= 300π
L.S.A. of cones = 2[πr]
= 2[π × 5 × 13]
= 130π
T.S.A. of remaining part
= 300π + 130π
= 430π