Question 1124848: A college student earned $7200 during summer vacation working as a waiter in a restaurant on the boardwalk at the beach. The student invested part of the money at 10% and the rest at 9%. If the student received a total of $680 in interest at the end of the year, how much was invested at 10%
The amount invested at 10% was
Answer by ikleyn(52788)   (Show Source):
You can put this solution on YOUR website! .
Let x = the amount invested at 10%.
Then the amount invested at 9% is the rest (7200-x) dollars.
The annual interest from the 10% account is 0.1x, while from the 9% account it is 0.09*(7200-x).
Your equation is
interest + interest = total interest, or
0.1x + 0.09*(7200-x) = 680.
Simplify and solve for x.
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It is a standard and typical problem on investments.
If you need more details, or if you want to see other similar problems solved by different methods, look into the lesson
- Using systems of equations to solve problems on investment
in this site.
You will find there different approaches (using one equation or a system of two equations in two unknowns), as well as
different methods of solution to the equations (Substitution, Elimination).
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lesson is the part of this online textbook under the topic "Systems of two linear equations in two unknowns".
Save the link to this online textbook together with its description
Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson
to your archive and use it when it is needed.
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