<PRE><B>Question 113310</B>
Sam&#39;s annual interest from an investment is 225. If Sam had invested $600 more at an annual interest rate that was 1% less, the annual interest would have been $234. What are the amount and rate of his actual investment?
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Interest = Prt; in your problem t=1
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EQUATIONS:
225 = Pr
234 = (P+600)(r-1)
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234 = Pr -P + 600r -600
234 = 225 -P + 600r -600
609 = -P + 600r
P -600r+609 = 0
But r = 225/P:
P -[600*225/P]+609 = 0
Multiply thru by P to get:
P^2 +609P - (600*225) = 0
Use the Quadratic Formula to solve for P:
P = [-609 +- sqrt(609^2 -4*(-600*225)]/2
P = [-609 + 954.4]/2
P = $172.70
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r = 225/P = 0.768
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Cheers,
Stan H.
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