Question

two cylinders have their radii in the ratio 4 is to 5 and their height in the ratio 5 is to 6 find the ratio of the csa

Answer 1

$\frac{r1}{r2} = \frac{4}{5} \\ \frac{h1}{h2} = \frac{5}{6} \\ \frac{csa1}{csa2} = \frac{2\pi \: r1h1}{2\pi \: r2h2} \\ = \frac{4}{5} \times \frac{5}{6} \\ = \frac{2}{3}$