Question

A water main for a street is being laid using mechanical joint pipe. the pipe comes in 18-foot and 20-foot sections, and a designer determines that the water main would require 14 fewer sections of 20-foot pipe than if 18-foot sections were used. find the total length of the water main.

Answer 1

Let

x--------> the total length of the water main

we know that

the number of 20 ft pipes is x/20

and

the number of 18 ft pipes is x/18

Since they differ by 14 pipes,

we have the equation

x/18 - x/20 = 14

Solve for x (by canceling fractions)

20x - 18x = 14*18*20

x = (14*18*20)/2

x = 2,520 ft

therefore

the answer is

the total length of the water main is 2,520 ft

Answer 2

To solve this problem you must apply the proccedure shown below:

1. You can write the following expression, where the variable $x$ is the total length of the water main:

$\frac{x}{18}-\frac{x}{20}=14$

2. Now, solve for $x$, as following:

$\frac{10x-9x}{180}=14\\ x=(14)(180)\\ x=2520$

Therefore, the answer is: $2520 feet$