Cracking The Ap Calculus ab Exam 2018

The rule for finding the volume of a solid with known cross-sections is V = A(x) dx, where

A   is  the formula for the area    of  the cross-section.  So  x   represents  the diameter    of  a   semi-

circular    cross-section.

The area of a semi-circle in terms of its diameter is A = . We find the length of the

diameter    by  solving the equation    4x  +   5y  =   20  for y:  y   =    .  Next,   we  need    to  find

where    the     graph   intersects  the    x-axis.  You     should  get    x    =   5.  Thus,   we  find    the     volume  by

evaluating  the integral.

This integral can be simplified to

You can evaluate the integral by hand or with a calculator. You should get