Micheal Perez has a total of 2000 on deposit with two saving

Micheal Perez has a total of $2000 on deposit with two saving institutions. One pays interest at the rate of 3 percent per/year. The other 4 percent per/year. If he earned a total of $72 in interest during a single year, how much does he have on deposit in each institution?

Solution

Let

x = deposited at 3%
2000 - x = deposited at 4%

Thus,

x(0.03) + (2000-x)(0.04) = 72

0.03x + 80 - 0.04x = 72

-0.01x = -8

x = 800
2000-x = 1200

Thus, he deposited $800 at 3%, and $1200 at 4%. [ANSWER]