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ren
New Member

USA
1 Posts

 Posted - 09/10/2007 :  13:41:40 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 4.5Please explain in terms of pairs of lenear equation.

the_hill1962

USA
1468 Posts

 Posted - 09/10/2007 :  14:03:58 Let c=amount of cementand g=amount of gravelSo, "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=22.5You can substitute "4c" for "g" into the cg=22.5 since g=4c.See how it works------c+g=22.5 becomes c+4c=22.5Now that simplifies to 5c=22.5 which means c=4.5and 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
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