[Guest]

Hello Forum,

I kept reading and reading this word problem below, but I still couldn't come up with any plan to solove it. Can you please break it down for me. All I know is that I need to find "the total length of the water main". So I figure that I need to find the parts. That is where I got stuck. I keep seeing that the total length of the main is 20 feet long, but that is not a correct answer.

A water main for a street is being laid using a particular kind of pipe that comes in either 18-foot sections or 20-foot sections. The designer has determined that the water main would require 10 fewer sections of 20-foot pipe than if 18-foot sections were used. Find the total length of the water main.

[Guest]

You are correct, you need to find the total length. How did you come to 20ft?

What the question is saying is that the length is:

x * 18 ft long AND that it's also (x-10) * 20ft long.

Can you do algebra?

[Guest]

You are correct, you need to find the total length. How did you come to 20ft? What the question is saying is that the length is: x * 18 ft long AND that it's also (x-10) * 20ft long. Can you do algebra?

Hmmm, well thank you for trying to help me, though, Oboe Passion. I was hoping for a more thorough detailed explanation. I think my major problem is that I didn't realize or understand that "18-foot sectons or 20-foot sections" refers to the length of each of the section. If I had understood that piece of information, I would have used simple multiplication to find the total length. Another level of difficulty for me was that I didn't understand that the problem was setting up the length of pipe with the 18-foot sections is the same to the length of the pipe with the 20-foot sections.

So I guess, if I let X to be the number of pipe length of the pipe with the 18 foot sections, then X - 10 would be the number of pipe length of the pipe with the 20 foot sections. So the total length of 18-foot sections pipe = 18x, and the total length of the 20-foot sections pipe = 20 (X-10). Since both pipes have the same length, the equation should be

18x = 20(x-10) or X = 1000 feet. So the total length would be 8(1000) or 8,000 feet long.

[Thalia]

Hmmm, well thank you for trying to help me, though, Oboe Passion. I was hoping for a more thorough detailed explanation. I think my major problem is that I didn't realize or understand that "18-foot sectons or 20-foot sections" refers to the length of each of the section. If I had understood that piece of information, I would have used simple multiplication to find the total length. Another level of difficulty for me was that I didn't understand that the problem was setting up the length of pipe with the 18-foot sections is the same to the length of the pipe with the 20-foot sections.

So I guess, if I let X to be the number of pipe length of the pipe with the 18 foot sections, then X - 10 would be the number of pipe length of the pipe with the 20 foot sections. So the total length of 18-foot sections pipe = 18x, and the total length of the 20-foot sections pipe = 20 (X-10). Since both pipes have the same length, the equation should be

18x = 20(x-10) or X = 1000 feet. So the total length would be 8(1000) or 8,000 feet long.

Not quite. Where did you get the 8 from? Let's start with the equation you have.

18x(number of 18-foot pipes)=20(x-10 sections of pipe)

Using the distributive property, we get 18x=20x-200

Solving for x, we get -2x=200 x=100

Substitute 100 for x in the term 18x. 18*100=1800

[Guest]

Not quite. Where did you get the 8 from? Let's start with the equation you have.

18x(number of 18-foot pipes)=20(x-10 sections of pipe)Using the distributive property, we get 18x=20x-200 Solving for x, we get -2x=200 x=100 Substitute 100 for x in the term 18x. 18*100=1800

God job as always, Thalia. Thanks for fine tunning my equation solving skills.

[Thalia]

No problem! I've gotten to the point where algebra seems rather fun. Algebra never asked me to carbon date a tree that fell when Mount Mazama erupted. =.='

Edited February 2, 2011 by Thalia