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n, divided by 5

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n, divided by 5

by sanju09 » Fri Jul 23, 2010 3:27 am
If a positive integer n, divided by 5 has a remainder 2, which of the following must be true?
I n is odd
II n + 1 cannot be a prime number
III (n + 2) divided by 7 has remainder 2
A. none
B. I only
C. I and II only
D. II and III only
E. I, II and III

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by kvcpk » Fri Jul 23, 2010 3:29 am
sanju09 wrote:If a positive integer n, divided by 5 has a remainder 2, which of the following must be true?
I n is odd
II n + 1 cannot be a prime number
III (n + 2) divided by 7 has remainder 2
A. none
B. I only
C. I and II only
D. II and III only
E. I, II and III

[spoiler]Source: majortests.com[/spoiler]
n = 5q+2
when q=2, n is even... I out
when q=2, n+1 = 13 is prime.. II out

hence pick A
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by selango » Fri Jul 23, 2010 4:00 am
n=5q+2

n=7,12,17,22..........

n is odd

n=12,Not true

n+1 cannot be a prime number

n=7,Not true

n+2 divided by 7 has reminder 2

n+2=7q+2

n=7,12,17,22..........

n+2=9,14,19,24..

9 divided by 7 gives remainder 2

14 divided by 7 gives remainder 0

Pick E
--Anand--
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