The radius of a circular ink spot on blotting paper is given by centimetres

MATHEMATICS · Subjective · AP · Calculus AB · Contextual Applications of Differentiation · Contextual Applications of Differentiation

Problem

The radius of a circular ink spot on blotting paper is given by

r(t)=1+0.5t^{2}

centimetres, where

t

is the time in seconds. Find the rate at which the area of the spot is increasing at

t=4\,\text{s}