percentage word problem

Question

jack and anita invested $6000 in two cd's last year. one cd paid 4% interest and the other paid 6% interest. at the end of a  year they earned $314 in simple interest. how much did they invest at each rate?

Answer 1

You're investing $6,000 in the two CDs. So call the principal amount in the first CD = "p", and the second amount would be $6000-p. The amount of interest you will have after one year, or $314, is equal to (0.04 * p) + (.06) (6000-p)

 

Now that everything is describe in one variable p, you can manipulate one equation to determine the answer.

.04p + .06(6000-p) = 314

.04p + 360 - .06p = 314

-.02p + 360 = 314

-.02p = -46

p = -46/(-.02) = 2,300

The amount invested in the second CD is 6000-p, or 6000-2300 = 3700