Question

a submarine left the surface of the water at rate of-2mper second. at thet rate how long will it take for submarine to reach - 80m level

Answer 1

A submarine take 40 seconds to reach 80m
2m = 1sec
80m = y


this is an instance of direct proportion
hence,
$\frac{1}{2 } = \frac{y}{80}$
$\frac{80 \times 1}{2} = y$