College Board blue book - question

Test Preparation SAT Preparation
1

<p>Alright, on test 1 section 3 pg 399 number 16, A seems like its an answer to me, but the book says just E. it seems like you can end up with 2x^3pie as the formula for whats given, choice A, and E, can somebody help to explain this?</p>

<p>EDIT: and if its not too much too ask could someone explain number 19 on page 400 too. thanks :)</p>

2

<p>the original cylinder is pi<em>x^2</em>2x which is 2(pi)(x^3)</p>

<p>a) is pi<em>(2x)^2</em>x which is 4(pi)(x^3)</p>

<p>e) is x<em>2x</em>(pi*x) = 2(pi)(x^3)</p>

<p>you probably forgot that (2<em>x)^2 = 4</em>x^2</p>