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by Neo2000 » Thu Jun 14, 2007 6:25 pm
18??

Re-arranging you will get (10X +20Y)/(X+Y) = 10 +10Y/(X+Y)

Now X+Y = 10
1,9
2,8
3,7
4,6

Only 2,8 matches the answer options
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by dunkin77 » Fri Jun 15, 2007 3:14 am
Thanks - yes, OA is D.

sorry...but
can you show me the process from 10X+10Y/(x+y) to 10+10y/(x+y)???


from there how to get 18?
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by jayhawk2001 » Fri Jun 15, 2007 6:02 am
dunkin77 wrote:Thanks - yes, OA is D.

sorry...but
can you show me the process from 10X+10Y/(x+y) to 10+10y/(x+y)???


from there how to get 18?
[ Cut-n-paste from my earlier post ]

The eqn can be reduced to

(10x + 20y) / (x+y) = k

10 + 10y/(x+y) = k

y / (x+y) will be > 0 and < 1 as we know x and y are positive. So,
discard A and E.

When x = y, y/(x+y) = 1/2 and when x = 0, y/(x+y) = 1. So, value of
y/(x+y) will vary between 1/2 and 1. So, discard B and C.

Only D remains.
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