Maths Gcse similarity please help

gapyear2018

X and Y are two geometrically similar solid shapes.

The total surface area for X is 450cm2
The total surface area for Y is 800cm2

The volume of shape x is 1350 cm

Calculate the volume of shape Y

The answer is 3200cm3 , but I don't understand how to get that answer. Please explain it. Thanks

Reply 1

gdunne42

Original post by ScienceFantatic

similar shapes are enlargements.
If the scale factor for enlarging corresponding lengths is x5 the scale factor for area is 5 squared and for volume it is 5 cubed.

You are given information that allows you to work out the scale factor for AREA = x(800/450) which simplifies to a nice exact fraction.

To work out the scale factor for length you need to square root the one for area.
To then find the scale factor for volume you need to cube the result for length.

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