I need help with an investment interest problem.

Question

I got 30,000 but didn't put the problem together right. Melissa invested a sum of money a 3% annual interest. She invested three times that sum a 5% annual interest. If her total yearly interest from both investments was 5400 how much was invested at 3%. I have the answer at 30,000 by dividing 5400 from .18, but dont know if I set it up right.

Answer 1

Here's how to set it up.

 

Income from first stream = Principal x .03

Income from second stream = Principal x 3 x .05

 

Add them together: Total income = Principal x .18

 

So $5400 = Principal x .18

 

So you did get the correct answer.  You just need to show your individual steps.