The simple interest on a sum of money invested at 5% per annum for 3 years was $90. The sum of money invested was

Sum of money = $600

Step-by-step explanation:

X = sum of money

Simple interest means that its the same percentage of interest for a given number of years.

The interest per annum is 5% for 3 years, so 5% x 3 = 15%

15% = 0.15 (as a decimal)

Now, we can put this into an equation:

0.15x = 90

x = 90 / 0.15

x = 600.

sum of money invested = $600