Question

I keep getting it wrong, can someone help?

Answer 1

This is half of a sphere on top of a cylinder.

Volume of a cylinder =
`\pi`
`r^(2)`h where r is the radius and h is the height.

You are given the diameter of the circle, so diameter/2 = radius.

For the cylinder, r = (18/2) = 9 and height is 13.

Volume of the cylinder =
`\pi 9^(2) *13` = 1053
`\pi` cubic meters

That top is just 1/2 of a sphere. The radius is also 9 (just divide the diameter by 2).

Volume of a sphere is
`(4)/(3)\pi r^(3)`.

=
`(4)/(3)\pi 9^(3)`

=
`(4)/(3) \pi 729\\= 972\pi` cubic meters BUT REMEMBER we just want 1/2 because the top is just 1/2 of a sphere.

so 972
`\pi`/2 = 486
`\pi` cubic meters

Add them up!

1053
`\pi`+ 486
`\pi` = 1539
`\pi` cubic meters