2. If a diver breathes through 100 bar of air in 30 minutes at a depth of 30 meters. How much will they breathe through in 15 minutes at 20 meters if all other factors remain the same?

D) 37.5 bar

There are 2 Variables changing. The DEPTH is one variable the amount of TIME is another variable. So we need to do calculate the impact both these changes is variables have. It does not matter which order we do the calculations in. I am going to deal with the change in time first. In the VIDEO I show how to do it changing the depth variable first.

30 minutes is the time at the first depth. 15 minutes is the time at the second depth. So the amount of time is half, therefore, the amount of air (bar) that i will breathe through is half. 100bar divided by 2 is 50bar.

Now I will deal with the change in depth. Using the amount of bar I have adjusted to for the change in time 50bar.

I start at 30m or 4ata. How many bar will i breathe through at the surface? Less for sure! So I DIVIDE 50 by 4 to work out what i will breathe through at the surface. 50/4 is 12.5bar AT THE SURFACE. The second depth is 20m or 3ata. So now I multiply by 3 to work out the amount i would breathe at 20m. 12.5 x 3 = 37.5 bar.