Question

The expression -370+13m represents a submarine that began at a depth of 370 feet below sea level and ascended at a rate of 13 feet per minute. What was the depth of the submarine after 9 ​minutes?

Answer 1

Depth after 9 minutes is -253 feet

Explanation:

Since we can find the submarine's depth as a function of time, m (in minutes), lets use the function to calculate the answer.

We are given the equation for depth: Depth(m) = -370+13m

Depth(x) means that the equation will tell us the submarine's depth after m minutes. The equation is missing the units, but we know from the statement that the initial depth is -370 feet and the rate of ascention is +13 feet/min. So we can enhance the equation by rewriting it with the units.

Depth(m) = -370ft+13(feet/minute)*m [m is minutes]

The sub's depth after 9 minutes is:

Depth(9) = -370ft+13(feet/minute)*(9 minutes)

Depth(9) = -370ft + 13*(9)

Depth(9) = -370+117

Depth(9) = -253 feet