A rectangular prism-shaped container has a cross-sectional area of 42cm squared. If 1680cm cubed of water is poured into the container, what is the height of the water in it?
If we just look at the shape of the water, we see also a rectangular prism....
The cross sectional area of this prism is also 42 cm2 .
And...
volume of prism = (area of cross section) * (height)
Plug in the information from the problem.
1680 cm3 = (42 cm2) * (height)
Divide both sides by 42 cm2 .
40 cm = height