SOLUTION: Equal amounts are invested at 2%, 7%, and 9% annual interest. If the three investments yield a total of $720 annual interest, find the total investment.

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Question 1121637: Equal amounts are invested at 2%, 7%, and 9% annual interest. If the three investments yield a total of $720 annual interest, find the total investment.
Found 3 solutions by solver91311, greenestamps, ikleyn:
Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!


Let represent one-third of the total investment. Then



Solve for , then calculate .


John

My calculator said it, I believe it, that settles it
Answer by greenestamps(13200)   (Show Source): You can put this solution on YOUR website!


If the amounts are the three rates are equal, then the average rate of return is the average of the three percentages.

(2+7+9)/3 = 18/3 = 6

x amount invested at 6% yields $720:



Solve....
Answer by ikleyn(52797)   (Show Source): You can put this solution on YOUR website!
.
Let x be the unknown value of equal amounts invested at 2%, 7% and 9%.


Then your equation is


    0.02x + 0.07x + 0.09x = 720 dollars,   or


    0.18x = 720,


    x =  = 4000 dollars.


Answer.  The value of each of the three equal amounts is $4000.


Check.   0.02*4000 + 0.07*4000 + 0.09*4000 = 720 dollars.   ! Correct !

Solved.


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