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2^100-2^96

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Junior | Next Rank: 30 Posts
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2^100-2^96

by Hano » Wed Dec 05, 2007 10:41 pm
What is the greatest prime factor of 2^100 - 2^96?
A. 2
B. 3
C. 5
D. 7
E. 11

What is a good approach to this?
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by samirpandeyit62 » Wed Dec 05, 2007 10:46 pm
IMO a good approach is to extract the common part in both the exponents & then work with the problem, In fact this step will itself present the soln

i.e 2^100 - 2^96?

2^96 ( 2^4- 1)

=2^96(15)

=2^96 (5*3)

ans 5 C
Regards
Samir
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Junior | Next Rank: 30 Posts
Posts: 29
Joined: Sat Nov 10, 2007 6:49 pm

by Hano » Thu Dec 06, 2007 8:12 pm
nice, thanks.
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