redo#2 using compound discount instead of simple interest. Find the amount which must be invested at a rate of simple interest of 9% per annum in order to accumulate $ 1000 at the end of 3 years. Solution 1000 = P*(1 +9/100)^3 P = $772.20 by simple interest rate: 1000 = P(1 +9*3/100) P = $787.40.