Question

Last year, Deshaun 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 $1440 in interest. How much did he invest in each account?

Answer 1

the amount Deshaun invested in an account that paid 9% interest = $9,000

the amount Deshaun invested in an account that paid 5% interest = $11,000

Explanation:

Let x = the amount Deshaun invested in an account that paid 9% interest

Let y = the amount Deshaun invested in an account that paid 5% interest.

Thus;

x + y = 20,000 - - - - (eq 1)

Now, After one year, he received a total of $1440 in interest. Thus;

0.09x + 0.05y = 1440

Multiply each term by 100 to give;

9x + 5y = 144000 ---- (eq 2)

Making x the subject in equation 1,we have;

x = 20,000 - y

Putting 20,000 - y for x in eq 2,we have;

9(20,000 - y) + 5y = 1440

180000 - 9y + 5y = 144000

180000 - 4y = 144000

180000 - 144000 = 4y

36000 = 4y

Divide both sides by 4 to give;

y = 36000/4

y = $9,000

x = 20,000 - 9000

x = $11,000