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In a particular town, an Internet service provider used to have 18017 dial-up customers about 3 years ago. Now it has 5874 dial-up customers. What is the total percent decrease in the number of dial-up customers in this town?

The total percent decrease is

Solution

To calculate the percentage decrease, first we find the amount of decrease by doing a simple subtraction calculation, and then we find the percentage decrease.

In this problem, the amount of decrease is $18017 - 5874 = 12143\text{.}$

Since there were initially 18017 dial-up customers, we need to ask: 12143 is what percent of 18017?

Let the decrease 12143 be $x$ (as a percent) of 18017. That means:

$\begin{aligned} 12143 \amp= x \cdot 18017\\ \frac{12143}{5874} \amp= \frac{x \cdot 18017}{18017}\\ \frac{67.3974579563745}{100} \amp= x\\ x \amp=67.40 \% \end{aligned}$

There has been a 67.40% decrease in dial-up customers in the town over this three-year period.