simple interest

Question

A person had 18,000 in two accounts, one paying 9% simple interest and one paying 10% simple interest. How much was invested in each account if the interest after one year is 1,716?

Answer 1

So you have 2 accounts that total $18,000. Let's call the one with 9% interest X and the 10% Y. Since their total is $18,000 your first equation is X + Y = 18,000.

 

Your second equation will focus on the simple interest after one year. You can multiply the amount in each account by the percent associated with it. Together that gives you a total interest of $1,716. Your second equation is (.09)X + (.10)Y = 1,716. 

 

Use substitution method to get to this step:

 

(.09)X + (.10)(18,000 - X) = 1,716

 

Now isolated and solve for X.

 

X = 8,400

 

Subtract that amount from 18,000 to find Y.

 

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