Chapter 7, Problem 9CST

To determine

To calculate: The new amount.

Answer to Problem 9CST

The new amount is $50$ .

Explanation of Solution

Given information:

The information given in the question:

Old amount = $\text{40}$

Percent of increase = $25\%$

Formula used:

The percent of change is the ratio of the amount of increase or decrease to the original amount.

Percent of change,

  $p\%=\frac{\text{amount of increase or decrease}}{\text{original amount}}$

Calculation:

As per the problem,

Original amount = $\text{40}$

Percent of increase = $25\%$

Calculate amount of increase

Write formula,

  $p\%=\frac{\text{amount of increase or decrease}}{\text{original amount}}$

Substitute $25\text{ as }p\text{ and 40 as original amount}$

  $\begin{array}{l}25\%=\frac{\text{amount of increase }}{40}\\ \frac{25}{100}=\frac{\text{amount of increase }}{40}\text{ [write percent as fraction]}\\ \text{40}\cdot \frac{25}{100}=\frac{\text{amount of increase }}{40}\cdot 40\text{ [multiply each side by 40]}\\ \text{10 = amount of increase [simplify]}\end{array}$

Now,

New amount = original amount + amount of increase

New amount = $40+10=50$ [substitute the values for original amount and amount of increase, and add]

Hence,

New amount is $50$ .