Q9 of 79 Page 238

Radius and slant height of a cone are 20 cm and 29 cm respectively. Find its volume.

GIVEN : radius of cone “r” = 20cm


Slant height of cone “l” = 29cm


we take π =


TO FIND : volume of the cylinder “V” = ?


PROCEDURE :


As we know that, volume of cone “V” = × π r2h


As we are not given the value of h, we have to find it.


As it is a right cone, l2 = r2 + h2


h2 = l2 – r2


= (29)2 – (20)2


= 841 – 400


= 441


h2 = 441


h = √ 441 = 21cm


So now, we put the values of r and h in the above formula


We get, V = × π r2h


= × π × (20)2× (21)


= × × 400 × 21


= 8800


∴ volume of the given cone = 8800cm3


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