<PRE><B>Question 157023</B>
On the basis of her horse’s age, weight, and workload, she determines that he needs to eat 15 lb of feed per day, with an average protein content of 8%. Hay contains 6% protein, whereas grain has a 12% content. How many pounds of hay and grain should she feed her horse each day?
:
Let x = amt of hay required
let y = amt of grain
:
From the information we can make two equations:
:
The total weight equation
x + y = 15
x = (15-y); can be used for substitution in this form
:
The per cent protein equation
.06x + .12y = .08(15)
:
Substitute (15-y) for x in the above equation, find y:
.06(15-y) + .12y  = .08(15)
:
.9 - .06y + .12y = 1.2
:
-.06y + .12y = 1.2 - .9
:
.06y = .3
y = {{{.3/.06}}}
y = 5 lb of grain
and
15 - 5 = 10 lb of hay
;
:
you can check our solutions in the original equation</PRE>