the_hill1962
Advanced Member
USA
1469 Posts 
Posted  09/10/2007 : 14:03:58

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 worksc+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 

