A rectangle has width $x$ cm and length $(2x+1)$ cm. Its width increases at $0.5\text{ cm/s}$.

Question

A rectangle has width $x$ cm and length $(2x+1)$ cm. Its width increases at $0.5\text{ cm/s}$. Find the rate of increase of its area when $x=3$.

Accepted Answer

$\frac{\mathrm{d}A}{\mathrm{d}t}=\frac{13}{2}\text{ cm}^2/\text{s}$.

Differentiation