Maths Help

[HQGTS74]

hi guys, need help with a question that seems quite simply but i cant do it.:mad: Anyway this is the question and i would appreciate help on how to do it. The answer is 960cm2.

A pyramid with total surface are of 120cm2 has its side lengths increased by a scale factor of 2. Whats the new surface area? Well answer is 960cm2 but dont know how to do it?
Thanks in advance
Chris

[wayno]

Might sound like a silly question but I assume it's a square based pyramid?

[HQGTS74]

Thats what i wasnt sure about?:o All it says is pyramid so i would assume triangular based because if side lengths are increased by 2 im sure they're all the same side lengths? If it was square based then it would be very hard to work out. This is meant to be a one minute question..
Chris

[stephenhrt]

Assuming a square pyramid, you have one face surface SA=0.5bh. If the height (h) is doubled it becomes 0.5b(2h). You have this four times, increase factor of 2 by 4 sides = 8. Thus 120sqcm times 8 = 960sqcm.

For triangle one it would be 6 times 120 sqcm = 720sqcm.

Hope this help

[minh427]

This may sound stupid but i think side length refers to the middle height section of the triangle face. So there are four sides and each is increased by 2,that becomes 8, then 8 times 120 = 960.

Im not sure but that is what i reckon.