Janet invested $6,000, part at 14% and part at 13%. IF the total interest at the end of year is $820, how much did she invest at 14%?

Answer 1

I did this by trial and error. There might be an easir way, but I don't know what it is.
I tried spitting it in half, but 14% of 3000 is 420 and 13% of 3000 is 390 but the total is too low. So I tried 4000 at 14% and 2000 at 13%. That happens to work. Calculate it to be sure! Good Luck!

Answer 2

let the amount invested at 14% be x,
then the amount invested at 13% would be 6000-x

clearly then

0.14x + 0.13(6000-x) = 820

14x + 13(6000-x) = 82000

easy to solve....