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integers : source - kaplan

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Source: — Problem Solving |

by outreach » Fri Jul 23, 2010 12:00 am
diff between 2 odd num is an even num..
hence the smallest value of a - b = 8
so a - x (where x = b-1) = 8+1 = 9

is it c?
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by singhpreet1 » Fri Jul 23, 2010 12:52 am
outreach wrote:diff between 2 odd num is an even num..
hence the smallest value of a - b = 8
so a - x (where x = b-1) = 8+1 = 9

is it c?
that is correct: 11-3=8 is the right answer.

Preet
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by jsasipriya » Fri Jul 23, 2010 6:19 am
yes. OA is C

Can you explain it please?
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by kvcpk » Fri Jul 23, 2010 6:32 am
jsasipriya wrote:If a and b are odd integers such that a - b > 7, what is the smallest possible positive difference between a and an even number less than b ?

7
8
9
10
11
Since a and b are odd,
let a= 2p+1
Let b = 2k+1

2p+1-2k-1>7
2p-2k>7

Even number less than b is 2k
So, we need 2p+1 -2k

Let u sgo back to our eqtn 2p-2k>7
Hence 2p+1-2k>8
Hence smallest possible difference should be 9

Hope this helps!!
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by sakali » Fri Jul 23, 2010 11:30 am
I got C as well...but I just plugged in numbers to get the answer.

kvcpk
Can you please elaborate on how you went from
2p-2k>7
to
Hence 2p+1-2k>8
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by kvcpk » Fri Jul 23, 2010 2:22 pm
sakali wrote:I got C as well...but I just plugged in numbers to get the answer.

kvcpk
Can you please elaborate on how you went from
2p-2k>7
to
Hence 2p+1-2k>8
Its simple. Added 1 on both sides to 2p-2k>7
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