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December 21, 2014

December 21, 2014

Posted by **mary** on Monday, April 18, 2011 at 12:37pm.

Book answer is 100.53cm^2 I came up with 150.79cm^2

my work:

2rr(4)6)=150.79cm^2 What did I do wrong??

- Geometry -
**MathMate**, Monday, April 18, 2011 at 1:34pmThe book answer is correct.

There are two things you need to watch for:

1. The diameter is 4 cm means the radius is 2 cm.

For the formula 2πrh, you have substituted 4 for the radius, which therefore gave twice the value it is supposed to have, namely 75.40 sq.cm.

2. The other 25.13 comes from the area of the two ends, each given by πr². (Note: r=2 cm).

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