# need help on setting up a formula

• Aug 12th 2009, 06:01 PM
Vicky1997
need help on setting up a formula
Most of Conservative Casey's money was put into a savings account that
paid 5% interest a year, but some of it was put into a risky stock fund that paid 16% a year. Casey's total initial investment in the two acounts was \$10000. At the end of the first year, Casey recieved a total of \$775 in interest from the two accounts. Find the amount invested in each.

I did guess and check. Started out with 8000 and 2000 got 720 in interest. then I tried 7500 and 2500 and got the answer 775.
Getting tired of guessing all the time. I wish I was better at algebra.(Crying)

How can I solve this with algebra?

Vicky.
• Aug 12th 2009, 06:20 PM
pickslides
x is the amount invested in the savings account, y is the amount invested in the risky stock, therefore...

\$\displaystyle x+y= 10000\$

\$\displaystyle 1.05x+1.16y= 10775\$

Can you solve these now?
• Aug 12th 2009, 06:24 PM
Vicky1997
Thank you.!!!!!!!!!!!

I see I can substitute Y for 10000 - X and then solve for X.

Vicky.(Rofl)
• Aug 12th 2009, 07:05 PM
Wilmer
Or you can take a shorter route; one variable only:

Let x = 5% amount; then 10000 - x = 16% amount
Then:
.05x + .16(10000 - x) = 775