Question

Equal amounts are invested at 3%, 7%, and 8% annual interest. If the three investments yield a total of $720 annual interest, find the total investment.

Answer 1

Answer: $12000

Work Shown

I'll assume simple interest is used.

x = amount invested per account

0.03x = yield from the 3% account

0.07x = yield from the 7% account

0.08x = yield from the 8% account

0.03x+0.07x+0.08x = 0.18x = total yield

0.18x = 720

x = 720/0.18

x = 4000 dollars is invested per account. There are 3 accounts, which gives a total of 3*4000 = 12000 dollars total invested.