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Old 2009 July 15th, 10:52 PM   #15 (permalink)
india_chintan
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Join Date: Apr 2009
Location: india
Posts: 110
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Quote:
Originally Posted by dissa View Post
hmm.. b/n between? I didn't get it.

My answer is here,
h(n) = 2 x 4 x .....n
h(100) = 2 x 4 x ...100
h(100) + 1 = (2 x 4 x ...100 + 1) = 2^50 (1 x 2 x...50) +1

if we divide this any number below 50;
1 would be the remainder. So that the smallest prime factor would be greater than 50.

answer (E)

I will elaborate on this more to make it simple.

h(n) = 2 x 4 x .....n
h(100) = 2 x 4 x ...100

Since there are 50 even nos. in 1-100 we can write:
h(100) = 2^50 *(1x2x3x4...50)

now, h(100) will be divisible by each nos. from 1 to 50 as it is in the numerator.

but, h(100) + 1 = (2 x 4 x ...100 + 1) = 2^50 (1 x 2 x...50) +1

with 1 added to it these prime nos. cannot divide the nos. in simpler terms if A can divide B, A cannot divide B+1. say 2 can divide 10, but cannot divide 11.

Coming back to the problem, since h(100) is divisible by all prime nos. from 1-50, the no. which can divide h(100)+1 has to be greater than 50.

Hence, the answer is E
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