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**Question**

13)

a) Calculate the volume of a sphere with radius 6cm.

a) Calculate the volume of a sphere with radius 6cm.

The volume

*V*of a sphere with radius*r*is**[2 marks]**

(b) An ornament is made from a solid glass square-based pyramid.

The base has side length 15cm.

A hemisphere with radius 6cm is cut out of the base of the pyramid.

This reduces the volume of glass contained in the ornament by 30%.

Calculate the perpendicular height of the pyramid.

**[5 marks]**