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Old 2006-10-19, 14:39   #2
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"The unspeakable one"
Jun 2006
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Divide into 2 sets, 1-50 & 51-100
Reverse the order of the second set
Imagine the second set written below the first set
Add each vertical pair (the pattern emerges), all pairs add to 101
Clearly there are 50 such pairs
Answer is 101*50

This is the arithmetic progression

Last fiddled with by retina on 2006-10-19 at 14:45 Reason: spoiler tags added
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