If height of a circular cone is decreased by 10% and its radius is increased by 10%, then what will be the change in its volume?

Increases by 8.9%.

Let the height and the radius of the cone = 10

Now according to the question,

                 Before          After

(Radius)²     100            121                       

Height         10                 9 

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Volume =   1000           1089 = 89 (Change)

%age change = 89 × \(\frac{100}{1000}\) = Increases by 8.9%.