Question

Fluffy laundry detergent reduced its regular size from 4.2 kg to 3.6 kg. The retail price dropped from $10.29 to $9.18. What was the percent change in the unit price?

Answer 1

Original Unit Price:

$10.29 / 4.2 kg = $2.45/kg

New Unit Price:

$9.18 / 3.6 kg = $2.55/kg

The price went up by $0.10/kg. If we compare that (divide that) by the starting unit price of $2.45, we get:

$0.10 / $2.45 ≈ 0.040816326530612

≈ 4.0816326530612 %

(You can round as accurately as your teacher needs.)