Question

Abby can buy an 8 pound bag of dog food for $7.40 or a 4 pound bag of the same dog food for $5.38. Which is the better buy?

Answer 1

Find how much cost one pound of dog food.

• If Abby can buy an 8 pound bag of dog food for $7.40, then one pound costs  $7.40:8=$0.925;
• If Abby can buy a 4 pound bag of dog food for $5.38, then one pound costs  $5.38:4=$1.345.

As you can see $0.925<$1.345, then the better buy is an 8 pound bag of dog food for $7.40, because the price for one pound is less.

Answer 2

One way to find out which bag is better to buy is to find out how much is 1 pound worth in both situations. So we have to divide the prices of 8 pound bag by 8 and 4 pound bag by 4:

$7.40 ÷ 8 = $0.925 per pound
$5.38 ÷ 4 = $1.345 per pound

1.345 > 0.925, so it's better to buy 8-pound bag