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Math Sets

by f2001290 » Wed Jun 13, 2007 6:46 am
If a and b are positive integers such that a – b and a/b are both even integers, which of the following must be an odd integer?

A. a/2
B. b/2
C. (a+b)/2
D. (a+2)/2
E. (b+2)/2
Last edited by f2001290 on Wed Jun 13, 2007 9:19 am, edited 1 time in total.
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by 800GMAT » Wed Jun 13, 2007 7:28 am
None:

a and b are both even. take a and b as any even integers to disprove the statements

A. a/2 = 4/2= 2
B. b/2= 8/2 =4
C. (a+b)/2 = 12/2 = 6
D. (a+2)/2 = (2+2)/2 = 4/2= 2
E. (b+2)/2= 6+2/2 = 8/2 = 4
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by f2001290 » Wed Jun 13, 2007 9:19 am
sorry - i modified the question.
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by ashok_uddaraju » Thu Jun 21, 2007 1:34 am
hi,

I would like to differ on this
My answer would be both D and E

a=8 b=4

a)a/2=8/2=4
b)b/2=4/2=2
c)(a+b)/2=(8+4)/2=12/2=6
d)(a+2)/2=(8+2)/2=10/2=5(odd)
e)(b+2)/2=(4+2)/2=6/2=3(odd)

Hope u agree with me
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by moneyman » Thu Jun 21, 2007 9:30 am
Since the question asks "must be true" its advisable to take two sets of values and work on it..

For example, take a=4 b=2 and a=8 and b=4 which are simple numbers which satisfy the condition stated in the question..

Substitute both of these values in each answer choice and you would find that only option (D) agrees to it..So the answer is (D)..Whats the OA?
Maxx
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