Question

I have $3,800 in two accounts for one year. The first account earns a yearly interest of 3.5%. The second account earns a yearly interest of 6%. How much money do I need to invest in the second account in order to earn $188 in interest from both accounts

Answer 1

-$1000

Explanation:

(3800 - x)*3.5/100 = (3800 + x)*6/100

(3800 - x)7/200 = 3/50(3800 + x)

3800 - x = 12/7(3800 + x)

3800 - x = 45600/7 + 12x/7

(19x + 19000)/7 = 0

19x = -19000

x = -$1000.

The minus implies that the investment must occur in the first account, not the second. It wouldn't make sense to add more money into the second account, because the second account already exceeds the $188 interest with the amount it has in there. Therefore $1000 must be added from the second account and invested into the first.