SOLUTION: Kate invested $9,000 one year ago. part of the money was invested at 6% and the rest at 10%. if the total interest earned in one year was $625.80, find how much was invested at eac

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Question 166848: Kate invested $9,000 one year ago. part of the money was invested at 6% and the rest at 10%. if the total interest earned in one year was $625.80, find how much was invested at each rate.
Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
Principal times (% of Interest)=interest earned
we have to break the left hand side of this equation into two parts, one at 6% and one at 10%. We know the Total principal is $9000 and we know the interest earned what we dont know is how much of the 9000 was invested at each rate
so lets call the principal invested at 6%=x therefore the principal invested at
10% is 9000-x. Now we can write a formula with one unknown remembering that 6% is .06 in decimal form and 10% is .10 in decimal form.


6%(x)+10%(9000-x)=625.8---->.06x+.1(9000-x)=625.8--->.06x+900-.10x=625.8
900-625.8=.10x-.06x--->.04x=274.2 x=6855
so highlight%28%246855%29 was invested at 6%
and amount invested at 10%=9000-6855=highlight%282145%29