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Infinite Sequence

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Infinite Sequence

by hansoo » Wed Jul 08, 2009 10:05 am
In the infinite sequence 13, 17, 21, 25, 29, . . . , where each term is 4 greater than the previous term, the 46th term is

a) 183
b) 187
c) 191
d) 193
e) 197

(poster's note: how fast can you answer this question? I'm guessing the average time is about one minute.)
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by mike22629 » Wed Jul 08, 2009 12:11 pm
13 + 45*4 = 193

IMO D.

20 seconds
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by nkanakiya » Wed Jul 08, 2009 6:05 pm
Line 1 Line 2
13 33
17 37
21 41
25 45
29 49

Last number on every line increases by 20..so on 9th line it will be 189 and will be 45th number. So 46th number will be 189+4 = 193...Bingo...
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by imhimanshu » Wed Jul 08, 2009 7:37 pm
193...20 secs at the max..

last term = a+(n-1)*d
= 13_(46-1)*4=193
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