Question

an advertisement claims that a 5-pound box of detergent will wash 20 loads of laundry. a 5-pound box costs $3.50. a 15-pound box costs $10.00. how much will you save per load if you buy the 15-pound box? round to the nearest tenth of a cent

Answer 1

A 5 pound box of detergent costs $0.175 per load ($3.50÷20). 
One load of laundry takes 0.25 pounds of detergent (5÷20). This means a 15 pound box can wash 60 loads of laundry (15÷0.25).
A 15 pound box costs about $0.167 per load ($10÷60).
Using a 15 pound box, you will save $0.008 per load ($0.175-$0.167).