Question
CBSEENMA9003519

If the lateral surface of a cylinder is 94.2 cm2 and its height is 5 cm, then find (i) radius of its base (ii) its volume. (Use straight pi = 3.14)

Solution

(i) Let the radius of the base of the cylinder be r cm.
              h = 5 cm
Lateral surface = 94.2 cm2
rightwards double arrow space space space space space space space space space space space 2 πrh space equals space 94.2

rightwards double arrow         2 x 3.14 x r x 5 = 94.2
         rightwards double arrow space space space space space space space space space space space space space space space space space space space space space space straight r equals fraction numerator 94.2 over denominator 2 cross times 3.14 cross times 5 end fraction
rightwards double arrow space space space space space space space space space space space space space space space space space space space space space space straight r space equals fraction numerator 94.2 over denominator 31.4 end fraction
rightwards double arrow space space space space space space space space space space space space space space space space space space space space space space straight r space equals space 3 space cm

Hence, the radius of the base is 3 cm.
(ii) r = 3 cm h = 5 cm
∴ Volume of the cylinder = πr2h
= 3.14 x (3)x 5 = 141.3 cm3.

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