testing header
Math Goodies is a free math help portal for students, teachers, and parents.
Free Math
Interactive Math Goodies Software

Buy Math Goodies Software
testing left nav
Math Forums @ Math Goodies
Math Forums @ Math Goodies
Home | Profile | Active Topics | Members | Search | FAQ
Save Password
Forgot your Password?

 All Forums
 Homework Help Forums
 Basic Math and Pre-Algebra
 application of lenear equation
 New Topic  Topic Locked
 Printer Friendly
Author Previous Topic Topic Next Topic  

New Member

1 Posts

Posted - 09/10/2007 :  13:41:40  Show Profile
In a certain concrete mix there was four times as much gravel as cement. The total volume of gravel and cement in the mix was 22.5 ft. How much of each was in the mix?

the answer is 18 and 4.5
Please explain in terms of pairs of lenear equation.
Go to Top of Page

Advanced Member

1469 Posts

Posted - 09/10/2007 :  14:03:58  Show Profile
Let c=amount of cement
and g=amount of gravel
So, "four times as much gravel as cement" means g=4c (how do you figure that the equation is g=4c ??? --- because there was more gravel, you multiply the amount of cement by 4).
The other equation is easy to get, "total volume is 22.5" means c+g=22.5
You can substitute "4c" for "g" into the cg=22.5 since g=4c.
See how it works------c+g=22.5 becomes c+4c=22.5
Now that simplifies to 5c=22.5 which means c=4.5
and since g=4c, g=44.5=18. Of course you need to indicate the unit

Edited by - the_hill1962 on 09/10/2007 14:11:11
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Topic Locked
 Printer Friendly
Jump To:
Math Forums @ Math Goodies © 2000-2004 Snitz Communications Go To Top Of Page
This page was generated in 0.07 seconds. Snitz Forums 2000
testing footer
About Us | Contact Us | Advertise with Us | Facebook | Blog | Recommend This Page

Copyright © 1998-2014 Mrs. Glosser's Math Goodies. All Rights Reserved.

A Hotchalk/Glam Partner Site - Last Modified 18 Dec 2014