Annie needs a new refrigerator and can choose between two models of the same size. One model sells for $525 and cost $0.08 per hour to run. A more energy-efficient model sells for $700 but runs for $0.05 per hour. If Annie buys the more expensive model, how long will it be before she starts saving money? a) What are we asked to find in this problem? Assign a variable to represent it. b) Write expressions in terms of your variable for the total cost incurred by each refrigerator. c) Write an equation and solve it. Solution for more efficient FC=700 , VC=0.05 for less efficient FC=525 , VC=0.08 h-hours total cost =700 +0.05*h before saving hours 700 +0.05*h=525 +0.08h h =5833 hrs .

1. Annie needs a new refrigerator and can choose between two models of the same size. One model
sells for $525 and cost $0.08 per hour to run. A more energy-efficient model sells for $700 but
runs for $0.05 per hour. If Annie buys the more expensive model, how long will it be before she
starts saving money?
a) What are we asked to find in this problem? Assign a variable to represent it.
b) Write expressions in terms of your variable for the total cost incurred by each refrigerator.
c) Write an equation and solve it.
Solution
for more efficient FC=700 , VC=0.05 for less efficient FC=525 , VC=0.08 h-hours total cost
=700 +0.05*h before saving hours 700 +0.05*h=525 +0.08h h =5833 hrs