Question 154717
 A new automobile engine can run on a mixture of gasoline and a substitute fuel. If gas costs $1.50 per gallon and the substitute fuel costs 40 cents per gallon, what percent of a mixture must be substitute fuel to bring the cost down to $1 per gallon?
:
Let x = percent of Substitute fuel
:
.40x + 1.50(100-x) = 100
:
.4x + 150 - 1.5x = 100
.4x - 1.5x = 100 - 150
-1.1x = -50
x = {{{(-50)/-1.1}}}
x = 45.45 % of substitute fuel
:
Check:
1.50 gas: 100 - 45.45 = 54.55
.40(45.45) + 1.50(54.55) = 
18.18 + 81.825 = 100.00
:
I am not absolutely sure about this. Let me know if I screwed this one up.  Carl