Question

A submarine begin the day to 240 m below sea level. It descended 40 m/h for three hours and then ascended 30 m/hrs. for five hours what was the position of the submarine after the 8 hour time period . Measured in meters

Answer 1

Descended total: -40×3=-120 meters
Ascended total: 30×5=150 meters

-240-120+150=-210 meters. As a result, the position of the submarine after 8 hours are 210 feet below the sea. Hope it help!

Answer 2

The submarine began 240 m below sea level.
If it descended 40 m every hour for three hours, we can calculate that the sub will be at 360 m below sea level. 
From here, the sub will rise 30 m every hour for five hours. By hour five, the sub would have already arisen 150 meters.
After these 8 hours, the sub should be 210 meters below sea level.