Question

Another submarine's descent can be represented as `y=-240x`, where u is the elevation and x is time in hours. How long will it take this submarine to make the descent (2,100 feet below the surface)?

Answer 1

The time it will take is 8hours 45mins.

Explanation:

Since y = –240x represents a submarine descent. We are looking for how long, that is the time, it will take for the submarine to make a descent of 2100. We know that y is the elevation, if it is descending it will be in the negative direction, making it -ve.

A descent of 2100 means y = –2100. Hence,

–2100 = –240x

x = –2100/–240 = 8.75hours = 8hours 45minutes. (0.75hours = 3/4hours = 3/4 x 60mins = 45mins).