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The denominator of a fraction is greater than the numerator by 1. If the fraction is increased by 1/12 if 2 is added to both the numerator and the denominator. What is the fraction?

 Oct 31, 2015
 #1
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x / [ x + 1 ]  + 1/12  =  [x + 2] / [ x + 1 + 2 ]    simplify

 

x / [ x + 1 ] + 1/12  = [x + 2] /[ x + 3]    simplify the left side

 

[ 12x + x + 1 ] /  [ 12 (x + 1)]  = [ x + 2] / [ x + 3]

 

[ 13x + 1 ] / [ 12x + 12] = [ x + 2] / [x + 3]         cross-multiply

 

[ 13x + 1] [ x + 3 ] = [ 12x + 12 ] [ x + 2 ]    simplify

 

13x^2 + 40x + 3   = 12x^2 + 36x + 24   

 

x^2 + 4x - 21  = 0      factor

 

(x + 7) (x - 3) = 0          x = - 7  or   x = 3

 

Check -7

 

-7 / [ -7 + 1 ]  + 1/12  =  [-7 + 2] / [ -7 + 1 + 2 ]   

 

-7 / [ -6] + 1/12  = [-5] / [-4]   ???

 

14/12 + 1/12  = 5/4

 

15/12 = 5/4     and that checks

 

Check 3

 

3 / [ 3 + 1 ]  + 1/12  =  [3 + 2] / [ 3 + 1 + 2 ]   =

 

3 / 4  + 1/12 =  5 / 6

 

9/12 + 1/12  = 5/6

 

10/12 = 5/6      yep....that works, too

 

So ..we get two answers......the fractions are   7/6   and 3/4 

 

 

 

cool cool cool

 Oct 31, 2015

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