The height of a square-based box is 4 cm more than the side length of its square base. If the volume of the box is 225 cm3. What are its dimensions?

So this is what I did:
v = l x w x h
v = 1x x 1x x (x+4)
v = 2x^2 + 8x

225 = 2x^2 + 8x
2x^2 + 8x - 225 = 0

Then I did the quadratic formula and got 8.8 as an x.

So I assume the side lengths are 8.8 and the height would be 8.8+4 so it would be 12.8.

I'm not sure if I did the equation correctly though. Thank you!

1 answer

First, Online, “*” is used to indicate multiplication to avoid confusion with “x” as an unknown.

V = x * x * (x+4)

You are adding instead of multiplying.

V = x^2 * (x+4) = x^3 + 4x^2