Equal amounts are invested at 4%, 7%, and 9% annual interest. If the three investments yield a total of $800 annual interest, find the total investment.

Question

Equal amounts are invested at 4%, 7%, and 9% annual interest. If the three investments yield a total of $800 annual interest, find the total investment.

Answer 1

a = one of the equal amounts

0.04a + 0.07a + 0.09a = 800

0.2a = 800

a = 400

 

Three investments of $400 was made. The total investment was $1,200.