Answers

2016-06-27T20:14:12+08:00
All numbers from 1 to 50 are integers
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2016-06-27T20:22:18+08:00
Sn= n/2 (a1 + an)
n=25
a1=1
a50=50
S50= 50/2 (1+50)
S50=25(51)
S50=1275

answer: 1275
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