Question

A pyramid with vertical height of 1ocm stands on a square base of sides 20cm .
a. Calculate to 3 significant figure for its total surface area.
b. If the pyramid is hollow what it's capacity in litres.

Answer 1

You don't say if in your surface ares you want to include the square base.
area of the 4 triangular sides:
need the height of one of them, 10^2 + 10^2= h^2
h = 10√2 cm
Area of one triangle = (1/2)(base)(height)
= (1/2)(20)10√2 = 100√2
add the area of the base which would be 400, if it should be included, you decide

vol = (1/3)(area of base)(height) <---- notice this height is the one given
= ....

Answer 2

I'm not sure what "1o" centimeters means. But here's the formula for the surface area of a pyramid:

B + (1/2)(ps)

where B=area of the base, p=perimeter of the base and s=slant height. Use the Pythagorean Theorem to find the slant height.

For part b, you'll need the formula for the volume of a pyramid. Here it is:

(1/3)Bh

where B=area of the base and h=vertical height. That's all the information you need to solve this yourself.