Equal amounts are invested at 5%, 7%, and 9% annual interest. if the three investments yield a total of $777 annual interest, find the total investment.

The total investment is $ 11100

Solution:

Equal amounts are invested at 5%, 7%, and 9% annual interest

Let x = amount invested at each interest

The three investments yield a total of $777 annual interest

5 % of x + 7 % of x + 9 % of x = 777

Solve the above equation for "x"

Thus each investment is $ 3700

Since three investments has been made,

Total investment = 3(3700) = 11100

Thus the total investment is $ 11100

391.6 is the correct answer