Question

John had 30,000 to invest. he invested part of his money and bonds paying 12 percent annual simple interest and the rest of the money in a savings account giving 4% annual interest at the end of the year, he received $2400 as extra income how much money did John place in each investment?

Answer 1

Let the amount that John placed in bonds be $x$. Then, the amount that he placed in the savings account has to be $\ 30,000 - x$. Using those as the investment amounts, the total extra income is given by adding the two separate interests as shown:

$.12x + .04(\ 30,000 - x) = \ 2,400$

We can now solve for x:

$.12x + .04(\ 30,000 - x) = \ 2,400$
$.12x + (\ 1,200 - .04x) = \ 2,400$
$.08x + \ 1,200 = \ 2,400$
$.08x = \ 1,200$
$x = \ 15,000$

Thus, the amount that John put in each investment is

Bonds: $x = \ 15,000$
Savings account: $\ 30,000 - x = \ 30,000 - \ 15,000 = \bf \ 15,000$