Oscar invests $20,000 in three investments earning 6% ,8% and 10%. he invests $9000 more in the 10% investment than in the 6% investment. how much does he have invested at each rate if he receives $1780 interest the first year?

This problem is mainly concerned with setting up an equation.

let's add the interest rates times their respective investment amounts:







simplify:



sum of interest:



1780 = (9000+x) 0.10 + x 0.06 + (11000-2x)0.08





solution:

He does not have any invested in the 6%, while he has 9000 invested at 10% and 11,000 invested at 8%

to check:





So this ended up being a trick problem because he does not actually have any invested in the 6% option.