A triangular pyramid has a volume of 840 cubic inches the triangular base has a base length of 20 inches and a height of 21 inches find the height of the pyramid

The answer is 2. You can find it by multiplying 20 and 21 giving you 420 and since 420 is half of 840 then all you would have to do is multiply 420 by 2 meaning the height is 2 since if you multiplied all in one it would be 20 x 21 x 2=840