A circular magnet has an inner radius x cm, an outer radius 2 cm larger and its depth is the same as the inner radius (as shown).
If the total volume of the magnet is 120 pi cm^3, find x

Start by writing an equation for the volume, then equate it to 120pi and then solve.

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Originally Posted by bosayna

A circular magnet has an inner radius x cm, an outer radius 2 cm larger and its depth is the same as the inner radius (as shown).
If the total volume of the magnet is 120 pi cm^3, find x

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Not clearly stated ( as there is no drawing shown as suggested) is if this is a magnet of x cm radius magnetic material with a coating of 2 cm non-magnetic material, or a magnet without an innercore of x cm radius. I assume the latter.

In that case just calculate the volume of a cylinder with a radius of x + 2 cm and a depth of x cm, and the volume of another cylinder with a radius of x cm and a depth of x cm, and deduct the smaller volume from the bigger one. The resulting value is equal to the given 120 pi cm^3 value.

From this you can solve x.

Success !

:)