Jan plans to invest $7500, part at 4% simple interest and the rest at 5% simple interest. What is the most that he can invest at 4% and still be guaranteed at least $325 per year?

Answer 1

part at 4% --- x
part at 5% --- 7500-x

.04x + .05(7500-x) = 325
after you multiply each term by 100 to get rid of the decimals this is an easy equation to solve.
Go for it.