Janice invests in a plan that has an APR of 2%. She invests three times as much in a plan that has an APR of 4%. If the total interest after one year from the investments is $644, how much was invested in each plan?

Solution:

First plan: x

Second plan: 3x

The equation is

2%*x + 4%*3x = 644

x = 4600

So

First plan: $4,600

Second plan: $13,800