Irene received $425 in annual interest on a principal investment sum of $5,000. What was the simple interest rate for his return?

Irene received 425 dollars as interest rate for his principal investment which is 5000 dollars.

Let's solve for the interest rate:

=> 425 / 5000 dollars = 0.085

=> 0.085 * 100% = 8.5%

Thus the simple interest or annual interest to her investment is 8.5%