Question 1206727
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A very different solution method than shown by the other tutors....<br>
Let x be the number of gallons he can buy at the regular price; then x+5 is the number of gallons he can buy at the reduced price.<br>
The cost of (x+5) gallons at 90% of the original price is equal to the cost of x gallons at the original price:<br>
{{{.9(x+5)=x}}}
{{{9(x+5)=10x}}}
{{{9x+45=10x}}}
{{{x=45}}}<br>
For $180, he could buy 45 gallons.  The original price per gallon was $180/45 = $4.<br>
ANSWER: $4<br>