Solve 5000*7%*9%?

Question

Dana is investing for his son's college fund. He put part of his $5,000 in an account that pays 7% and the remainder in an account that pays 9%. If he earned a total of $424.40 in interest after one year, how much did he invest in each fund? At 7%__________,at 9%__________________

Answer 1

a+b = 5000

0.07a+0.09b = 424.40

424.4a/5000+424.4b/5000 = (424.4)(5000)/5000 = 424.4

424.4/5000 = 0.08488

0.08488a+0.08488b = 1.07a+1.09b

0 = 0.07a-0.08488a+0.09b-0.08488b

0.01488a = 0.00512b

b = 2.90625a

a+2.90625a = 3.90625a = 5000

a = 1280

b = 3720

3720*.09 = 334.8

1280*.07 = 89.6

334.8+89.6 = 424.4

She invested $3720 in the account that paid 9% and $1280 in the account that paid 7%.

Answer 2

Dana invested $3720 in the account that paid 9% and  $1280 in the account that paid 7%.

Answer 3

424.40/5000 = 8.44%  So most of the money was in 9%!  8.44 being closer to 9 than 7.

.07x + .09y = 424.40

     x +     y = 5000

.07x/.07 + .09y/.07 = 424.40/.07

x + 9/7y=   424.40/.07

x  + 9/7y= 6062.8571

  x  + 9/7y= 6062.8571

- x   -     y= - 5000

        2/7y= 1062.8571

             y= 1062.8571/1/2/7

             y= 3719.99985



   5000 - 3720 = x

              1280 = x

7% yield is $1280

9% yield is $3720  

Thanks for the question....got the cobwebs out!  lol