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