invest $14000 into 2 accounts with different interest rates

Question

You Invest $14000 into two accounts.  one with a 4% interest rate and the other with a 7% interest rate.  after one year you have $840 in interest.  how much was invested in each?

Answer 1

Hi Brooke,

 

Let's say you invest "x" at 4% (or 0.04) then you have to invest the balance of the $14000 at 7% (0.07). That balance is "14000 - x". 

 

So if you invest x at 4% and 14000 - x at 7% anf you get 840 interest, your equation looks like:

 

x(0.04) + (14000-x)(0.07) = 840

0.04x + 980 - 0.07x    = 840 by distribution

-0.03x = -140

x = 4666.67   *** not sure if you are asked to round in your problem

then 14000 - 4666.67 = 9333.33

 

So 4666.67 is invested at 4% and 9333.33 is invested at 7%

 

you can always check by multiplying the amounts and their respective percentages to make sure you get to 840. 

4666.67 * 0.04 = 186.67 and 9333.33 * 0.07 = 653.33

If you add 186.67 and 653.33, you get 840.