Financial Algebra Word Problem

Question

Sam invests the earnings of $3000 from her full-time job. She invests part of the money at 5%/year, and the rest at 4%/year. After one year, these investments earn $140 simple interest. How much did she invest at each rate?  

What reason might you imagine for her to divide her money between two different accounts when she could obviously get more money in the one giving 5% interest?

Answer 1

x=money at 5% and y=money at 4%

x+y=3000

.05x+.04y=140

Multiply first equation by 5 and 2nd equation by 100

5x+5y=15000

5x+4y=14000

y=1000

x=2000