Question

Billy invested $18 of savings in two major business enterprises which paid interest at the rate of 3% and 6%, respectively. If his annual income for these two enterprises was equivalent to a return of 5% on the entire investment, find how much he invested at 3%.

Answer 1

$6

Explanation:

System of equations

x+y = 18

0.03x+0.06y = 5% of 18 = 0.9

(0.03x+0.06y=0.9)*100 = 3x+6y=90

(3x+6y=90)÷3 = x+2y=30

Substract (1)-(2)

x+2y=30 ... (1)

x+y=18 ... (2)

y=12

x+12=18

x=6

Thanks.