Math 0098
posted by Jazz on .
Last year, Joe had to invest. He invested some of it in an account that paid simple interest per year, and he invested the rest in an account that paid simple interest per year. After one year, he received a total of in interest. How much did he invest in each account?

Do you have numbers for this problem?

Last year, Joe had 10,000 to invest. He invested some of it in an account that paid 7% simple interest per year, and he invested the rest in an account that paid 9% simple interest per year. After one year, he received a total of $860 in interest. How much did he invest in each account?
(sorry bout that). 
x = amount in the first account
y = amount in the second account.
total invested:
x + y = 10,000
since Interest = Principles times rate times time.
.07x + .08y = 860
Now, you work with those two equations.
I would multiply the bottom equation by 100 to get rid of the decimals.
x + y = 10000
7x + 8y = 86000
Now, you can solve this by using the substitution method or the addition method.
I probably would use the addition(also known as the elimination method.)
Multiply the top equation by 7 and solve for y. Once you have y, you can find x. Then be sure to check x and y in both equations. 
where did you get .08 from?

Sorry.. the .08 is a typo. It should be .09
Which makes the equation 7x + 9y = 86000 
it would be 7x+7y=70000? I don't know how to solve the two equations

I don't think I'm doing this right because i am getting HUGE numbers like 156,000

7x 7y =70000
7x + 9y =86000
2y = 156000
divide by 2 and you get 7800 for y
so the other amount must be 2200.