Take our quiz to find out what your revision personality is! >>

gcse maths

dilsheen

can someone help me on how to do this question

(edited 1 year ago)

Reply 1

{Moss}

Original post by dilsheen

can someone help me on how to do this question

I may be completely wrong but I'd say if you say that 4*pi*radius^2 = 2*pi*radius*height + 2*pi*radius^2 (as surface areas are the same), we can simplify both sides by dividing by 2, and by r, and by pi, as they all share these to get 2r = height + r. Subtract r from both sides and we get the radius is equal to the height.

So you get a ratio of 1:1 from that, and if we test this, e.g. with 4, we get
64pi (4 squared times by 4) and 32 + 32 (for the other side) which is also 64. Note that a 1:1 ratio means they are the same, as we worked out.

So they're surface areas are the same for that, if we test again with 5 we get
100pi and (50+50)= 100.

So we cancelled it down, got that ratio of 1:1, and tested it just to make sure, and all returns well. I hope that makes sense? Best of luck!