If money is worth 12% effective, how often should paint B renewed so that it can be economical as paint A?

Question

The surface of a certain plant that requires painting is 8,000 sq.ft Two kinds of paint are available whose brand are A and B. Paint A cost P1.40 per sq. ft. but needs renewal at the end of every 4 years, while paint B cost P1.80 per sq.ft.
Please show me your formula or computation to prove that your answer is correct.. Thanks and God Bless You.

Answer 1

You need to calculate the cost per year per square foot for each paint, and compare the values. You can ignore the total square footage of the plant because it makes no difference. Paint A must be renewed every 4 years. Therefore, the cost per square foot per year is 1.4 / 4 = $0.35 per square foot per year. If Paint B must be renewed every x years, it would have a cost per square foot per year of 1.8 / x. So set 1.8 / x = 0.35 and solve for x.

I have no idea what "money is worth 12% effective" means.

Answer 2

Do your own homework.

And show up to class in your pajamas.