William opened two investment accounts.

Question

William opened two investment accounts. The first​ year, these​ investments, which totaled $2800​, yielded $129 in simple interest. Part of the money was invested at 5.5​% and the rest at 3​%. How much was invested at each​ rate?

Answer 1

.055x + .03(2800-x) = 129

.055x-.03x = 129 - .03(2800)

.025x = 129-84= 45

x = 45/.025 = $1800 at 5.5%

2800-1800 = $1000 at 3%

129 is 2800y

y= 129/2800= about 4.61% average interest rate on both investments

4.61 is closer to 5.5 than it is to 3, so we'd expect more invested at 5.5 than at 3