Please could somebody help me with this GCSE maths question?

I need to do this without a calculator because I'm estimating but I don't have a clue how to do it without one!

Q1 The volume of a sphere is given by the volume V=4/3pir^3

a) use this formula to estimate the volume of a sphere of radius 9cm

b) will your estimate be bigger or smaller than the actual value?

All help is appreciated 😁

When you estimate you round to 1 s.f.

so pi rounds to 3, and 4/3 pi rounds to 4

There are different schools of thought on what you do about 9^3 and you should check your notes to see which method you have been taught by your teachers.

Some will say that 9 is already to 1 s.f. so you should work with that. Others will say that the point of estimation is to work with numbers that are easily worked with, so round the 9 to 10 because that's easy to cube.

The important thing is to do it the way your teachers have taught you.