The regular price of a large bag of cat food is $12. Ike bought a bonus bag with 20% more than the large bag, and the bonus bag was on sale for $9. Ike then used a "$1 off coupon" when purchasing the bonus bag. What fraction of the regular price per ounce for the large bag did Ike pay for an ounce of food in the bonus bag? Express your answer as a common fraction.
+128408 Let the quantity in the large bag = Q oz
Then in the bonus bag the quantity = 1.2Q oz
Cost of large bag = $12
Cost of bonus bag = $8
Cost per oz in bonus bag = 8 / (1.2)Q
Cost per oz in large bag = 12 / Q
So
[8 / (1.2 Q) ] / [ 12/ Q ] =
8 / (1.2 Q) * Q / 12 =
8 / (12 * 1.2) =
8 / 14.4 =
80 / 144 =
5 / 9
