# A diver begins at sea level and descends vertically at a rate of 2 1/2 feet per second. How long does the diver take to reach -15.6 feet?

Nov 1, 2016

It takes the diver 6.24 seconds to reach the depth of -15.6 feet.

#### Explanation:

The formula for depth for a diver descending at a constant rate is:

$d = s + r \cdot t$ where $d$ is the new depth, $s$ is the starting depth, $r$ is the rate of change and $t$ is the time.

So substituting for what we know:

$- 15.6 = 0 + - 2.5 t$

$- 15.6 = - 2.5 t$

$\frac{- 15.6}{-} 2.5 = \frac{- 2.5 t}{-} 2.5$

$t = 6.24$