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Mr B has $20000 to invest. He invests part at 6% and the rest at 7%. He earns $1280 interest. How much did he invest at each of the rates?

 Feb 23, 2020
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Let   x  be  the amount  invested at 6%    and (20000 - x)  = the amount invested at 7%

 

We have  this equation  { Principal * Rate  = Interest }

 

.06x  + .07 ( 20000  - x)  =  1280    simplify

 

.06x  +  1400   - .07 x   =  1280

 

-.01x  +  1400   = 1280      subtract  1400 from both sides

 

-.01x  = -120      divide both sides by  -.01

 

x  =  $12000  =   amt  at 6%

 

20000 - x =  $ 8000   = amt at 7%

 

 

cool cool cool

 Feb 23, 2020

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