Chapter 6, Problem 27CR

To determine

The solution of the percent problem “What is 30% of 90?” with equation.

Answer to Problem 27CR

27

Explanation of Solution

Given:

The percent problem “What is 30% of 90?”.

Concept used:

To translate a phrase of the form “What is 30% of 90?” to an equation. First, assume that the number is x . Then, read the statement “ $A$ is $x\%$ of $B$ ”. In “ $x\%$ of $B$ ” the word “of” represents “multiplication”. So, the given statement can be translated in to an equation as follows:

  $\begin{array}{ccccc}\text{A}& \text{is}& \text{what percent}& \text{of}& B\\ \downarrow & \downarrow & \downarrow & \downarrow & \downarrow \\ A& =& x& ·& B\end{array}$

So, the equation becomes $A=x·B$ .

Calculation:

Using the concept, the given statement can be translated into an equation as

  $x=90·\frac{30}{100}$ .

Now, solve the equation as follows:

  $\begin{array}{c}x=90·\frac{30}{100}\\ x=\frac{2700}{100}\text{Mulitply both sides with 100}\text{.}\\ x=27\end{array}$

Conclusion:

The solution of the percent problem is27.