interest rates

Question

i need help

 

Mike invests $22,000 for a year. He invests some at the 7% interest rate and some at the 6% rate. After one year, he receives $1420 in total interest. How much did he invest at each rate?

Answer 1

Let x be the amount at 7%, then the rest would be (22000-x) at 6%

 

The interest for x at 7% is              0.07x

The interest for 22000-x at 6% is    0.06(22000-x)

 

The total interest is 1420, so your equation is 0.07x+0.06(22000-x)=1420

 

Solve for x to get the first amount, the rest should not be too hard!