Question 1044180
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An executive invests $30,000, some at 10% and some at 5%. If she receives an annual return of $2,200, how much is invested at 10%? 
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1. Solution with two unknowns


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Let t be an amount invested at 10%, and f be an amount invested at 5%. Then you have these to equations

   t +     f = 30000,
0.1t + 0.05f = 2200.

You can solve it by the substitution method or by the elimination method.
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2. Solution with one unknown


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Then your equation is 

0.1t + 0.05*(30000-t) = 2200,   or

0.1t + 5*300 - 0.05t = 2200,   or

0.05t = 2200-1500,   or

0.05t = 700,   t = {{{700/0.05}}} = 14000.
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<U>Answer</U>.  14000 invested at 10%,  16000 invested at 5%.