Mardi received an inheritance of 70000 She invested part at

Mardi received an inheritance of $70,000. She invested part at 12% and deposited the remainder in tax-free bonds at 11%. Her total annual income from the investments was $8200. Find the amount invested at 12%.

Solution

Suppose she invested = $X at 12% then

Total annual income is

0.12*X + (70000 - X)*0.11 = 8200

0.12*X - 0.11*X + 70000*0.11 = 8200

-0.01*X = (70000*0.11 - 8200)

X = -(70000*0.11 - 8200)/0.01

X = $50000