Chapter A.8, Problem 48AYU

To determine

To find: How much pure cement must be added to produce a cement mix that is $40\%$ cement?

Answer to Problem 48AYU

5 lb pure cement must be added.

Explanation of Solution

Given:

A 20-pound bag of Economy brand cement mix contains $25\%$ cement and $75\%$ sand.

Calculation:

$0.25\left(20\right)+1.00 x=0.40\left(20+x\right)$

Therefore,

$25\left(20\right)+100 x=40\left(20\right)+40x$

$60x=300$

$x=5\text{lb}$