Solve.
-Melissa invested a sum of money at 3% annual simple interest. She invested three times that sum at 5% annual simple interest. If her total yearly interest from both investments was $7200, how much was invested at 3%?
A)$40,000
B)$90,000
C)$270,000
D)$30,000

Question

Quizplus · Accepted Answer

Let the amount invested at 3% be x. Then, the amount invested at 5% is 3x. The total interest is given by 0.03x + 0.05(3x) = 7200. Simplifying, 0.03x + 0.15x = 7200, which gives 0.18x = 7200. Solving for x, x = 7200 / 0.18 = 40,000. Thus, $40,000 was invested at 3%.

Solve. -Melissa Invested a Sum of Money at 3% Annual Simple