Question 120042
If Ben invests $5000 at 5% interest per year, how much additional money must he invest at 6.5% annual interest to ensure that the interest he receives each year is 5.5% of the total amount invested? 
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Let x = amt of additional money he has to invest to accomplish this
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Here is the equation that we want:
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Money invested at 5% + Money invested at 6.5% = Total money at 5.5%
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.05(5000) + .065x = .055(x+5000)
250 + .065x = .055x + 275
.065x - .055x = 275 - 250
.01x = 25
x = 25/.01
x = $2500, additional money to be invested
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Check solution using our original equation:
250 + .065(2500) =
250 + 162.5 = 412.50
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.055(7500) = 412.50 confirms our solution
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That was pretty easy, right?