The question asks, For which design will the water pressure at the base of the dam wall be the greatest? The answer is all are equal.
This doesn't make sense to me.
Using the formula: P (pressure) = p (atmospheric pressure) + rho (density) * g (gravity) * y (depth below water surface)
What is confusing me is the y value, the depth below the surface. Yes both red points are the same depth below the water surface. But doesn't the red point in dam III only "see" a smaller column of water above it and so shouldn't it have less pressure on it than the red point in dam II?
Also, I know the formula would give the points at the base of dam I and dam II equal. But why doesn't the extra water in dam II (shaded in black) cause it to have a higher pressure at the base?