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"
[tex]5 \% \times x + 7 \% \times x + 9 \% \times x = 777\\\\\frac{5}{100} \times x + \frac{7}{100} \times x + \frac{9}{100} \times x = 777\\\\0.05x+0.07x+0.09x=777\\\\0.21x = 777\\\\x = \frac{777}{0.21}\\\\x = 3700[/tex]
Thus each investment is $ 3700
Since three investments has been made,
Total investment = 3(3700) = 11100
Thus the total investment is $ 11100
