Problema Solution
Last year Sung had $20,000 to invest. He invested some of it in an account that paid 9% simple interest per year and he invested the rest in an account that paid 5% simple interest per year. After one year he received a total of $1200 in interes. How much did he invest in each account
Answer provided by our tutors
Let's X be the amount in account that paid 9% and Y be the amount in the account that paid 5%.
Equation 1:
X + Y = 20000
Y = 20000 - X
Equation 2: Substitute Y = 20000 -X into Equation 2
(X x 0.09) + ( Y x 0.05) = 1200
(X x 0.09) + ((20000 - X) x 0.05) = 1200
0.09X + (1000 - 0.05X) = 1200
0.04X + 1000 = 1200
0.04X = 200
X = 200/0.04
X = 5000
Substitue X = 5000 into Equation 1
Y = 20000 - 5000
= 15000
Hence, he invested $5000 into the account that paid 9% simple interest and $15000 into the account that paid 5% simple interest