Question

A mother wants to invest ​$11,000.00 for her​ son's future education. She invests a portion of the money in a bank certificate of deposit​ (CD account) which earns​ 4% and the remainder in a savings bond that earns​ 7%. If the total interest earned after one year is $ 660.00, how much money was invested in the CD​ account?

Answer 1

First let's set the formula
0.04x+0.07 (11000-x)=660
Solve for x
0.04x+770-0.07x=660
0.04x-0.07x=660-770
-0.03x=-110
X=110÷0.03
X=3,666.67 round this answer
X=3667 invested in the CD account at 4%

The remainder is invested in the saving bond the earns 7% which is
11,000−3,667=7,333

Hope it helps!