9th Grade Math Problems

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Question : The sum of the age of two sisters is 31. The younger sister was 3 years younger than the older sibling five years ago. How old are they now?
asked Jul 2, 2013 in Algebra by smith ~Rookie~ (159 points)
    

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Best answer
Solution:
 
Let the age of two sisters x and y (Let us assume that y is younger sister).
 
Since sum of the age of two sisters is 31, So x + y = 31
 
x + y = 31  ............(1)
 
Five years ago:
 
The age of two sisters x - 5 and y - 5
 
Now 
y - 5 = (x - 5) - 3
 
y - 5 = x - 8
 
or y = x - 3   ....(2)
 
Substitute the value of y in equation (1)
 
x + x - 3 = 31
 
2x = 34
 
or x = 17
 
Again substitute the value of x in equation (2)
 
y = 17 - 3 = 14
 
Therefore both the sisters are of 14 and 17.
 
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answered Jul 2, 2013 by answermachine ~Rookie~ (120 points)
edited Jul 18, 2013 by answermachine

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