SOLUTION: Grace has $10,000 to invest. She invests some at 2.5% interest and the rest at 4% interest. How much should she invest at each rate to earn $310 in interest in one year?

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Question 1134714: Grace has $10,000 to invest. She invests some at 2.5% interest and the rest at 4% interest. How much should she invest at each rate to earn $310 in interest in one year?
Answer by ikleyn(52776) About Me  (Show Source):
You can put this solution on YOUR website!
.

0.04x + 0.025*(10000-x) = 310   dollars.


x = %28310-0.025%2A10000%29%2F%280.04+-+0.025%29 = 4000 dollars.


Answer.  $4000 invested at 4% and the rest $6000 invested ar 2.5%.


CHECK.   0.04*4000 + 0.025*6000 = 310 dollars.    ! Correct !

Solved.

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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.