Ratio Set-Up Problem
Date: 09/02/2003 at 23:15:08 From: Vanessa Subject: how to solve ratio problems Here is an example of a problem that I don't know how to set up: Concrete can be made by mixing cement, sand, and gravel in the ratio 3:6:8. How much gravel is needed to make 850 cubic meters of concrete?
Date: 09/03/2003 at 15:28:57 From: Doctor George Subject: Re: how to solve ratio problems Hi Vanessa, Thanks for writing to Doctor Math. We could think of this problem as having three variables, but with a little trick we can write it with just one. Let's define the amounts of material like this. cement = 3x sand = 6x gravel = 8x We don't know x yet, but can you see that the ratios are correct? The next step is to find x with this equation. 3x + 6x + 8x = 850 We can now solve for x, and then compute 8x to get the amount of gravel. Does that make sense? Write again if you need more help. - Doctor George, The Math Forum http://mathforum.org/dr.math/
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.