SOLUTION: If the price of gasoline increases by 20% and a person intends to spend only 8% more on gasoline, by how many percent should he reduce the quantity of gasoline that he buys?

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Question 984892: If the price of gasoline increases by 20% and a person intends to spend only 8% more on gasoline, by how many percent should he reduce the quantity of gasoline that he buys?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The person has bought +1+
gallon for price +p+
The price for the +1+ gallon
goes up to +1.2p+
------------------------
Let +x+ = the number of gallons he needs to buy
The person wants to pay +1.08p+
The price/gal is +1.2p%2F1+
[ price/gal ]x[ gal ] = [ price ]
+1.2p%2Ax+=+1.08p+
+x+=+1.08%2F1.2+
+x+=+.9+
+1+-+.9+=+.1+
+.1%2A100+=+10+
He must buy 10% less gasoline
----------------------------
check:
+.9%2A1.2+=+1.08+
OK