Logical thinking

Hot goIITian

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9 Jan 2011 12:15:48 IST
Posts: 155
9 Jan 2011 12:15:48 IST
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Logical thinking
Engineering Entrance , JEE Main , JEE Main & Advanced , academic , Miscellaneous

  There are 100 bulbs and each having separate switches and on at the initial stage.

 First man enters and switches off the bulbs, which are the multiples of 2.

 Next man enters and switches on the bulbs which are off and switches off the bulbs which are on, which are multiples of 3.

 Next man does the same as above for the multiples of 4.

 Next man does it for the multiples of 5.

 This process is repeated up to the multiples of 100.

 So finally how many bulbs will be glowing.

  Rate if the question is good.

 


Comments (19)


New kid on the Block

Joined: 9 Apr 2011 16:45:49 IST
Posts: 2
9 Apr 2011 17:04:22 IST
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answer is 10...

New kid on the Block

Joined: 12 Apr 2011 10:57:42 IST
Posts: 4
12 Apr 2011 11:08:23 IST
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a good questions. the answer is 91( ninety- one bulbs are glowing at the end). there are only 9 multiples of 100, if we go from 1 to 100 and these are: 1, 2, 4, 5, 10, 20, 25, 50 &100. so the last man switches off 9 bulbs, thus 91 remaining glowing

New kid on the Block

Joined: 12 Apr 2011 10:57:42 IST
Posts: 4
12 Apr 2011 11:11:57 IST
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a good question. the answer is 91( ninety- one bulbs are glowing at the end). there are only 9 multiples of 100, if we go from 1 to 100 and these are: 1, 2, 4, 5, 10, 20, 25, 50 &100. so the last man switches off 9 bulbs, thus 91 remaining glowing

New kid on the Block

Joined: 12 Apr 2011 10:57:42 IST
Posts: 4
12 Apr 2011 11:51:42 IST
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Sorry i was wrong. the calculations actually required much rough work. i agree with Rahul Pathaks's answer.

New kid on the Block

Joined: 16 Apr 2011 15:33:37 IST
Posts: 6
16 Apr 2011 17:17:25 IST
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i think....0 ball..becoz pf multiple of 100 at last...

New kid on the Block

Joined: 24 Aug 2007 16:26:40 IST
Posts: 24
21 Apr 2011 12:34:34 IST
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no. of bulbs glowing=no. of prime numbers from 1 to 100 is correct i think?

New kid on the Block

Joined: 3 Jun 2011 00:28:06 IST
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3 Jun 2011 00:44:08 IST
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55 bulbs

New kid on the Block

Joined: 3 Jun 2011 00:28:06 IST
Posts: 2
3 Jun 2011 00:44:48 IST
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the answer is 55

New kid on the Block

Joined: 7 Aug 2011 16:28:25 IST
Posts: 1
7 Aug 2011 16:28:25 IST
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all the square numbers

New kid on the Block

Joined: 28 Jun 2011 17:21:25 IST
Posts: 2
7 Aug 2011 23:35:29 IST
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1

New kid on the Block

Joined: 28 Jun 2011 17:21:25 IST
Posts: 2
7 Aug 2011 23:35:37 IST
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1

New kid on the Block

Joined: 7 Aug 2011 23:45:45 IST
Posts: 1
7 Aug 2011 23:45:45 IST
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All squares will be the answer:1,4,9,16,25....

Cool goIITian

Joined: 30 May 2010 14:25:42 IST
Posts: 48
8 Aug 2011 07:46:39 IST
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Yeah it's 9

New kid on the Block

Joined: 5 Aug 2011 11:03:21 IST
Posts: 8
9 Aug 2011 14:26:31 IST
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50 bulbs.

New kid on the Block

Joined: 5 Aug 2011 11:03:21 IST
Posts: 8
9 Aug 2011 14:28:26 IST
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Multiple of 2

New kid on the Block

Joined: 1 Sep 2011 22:06:13 IST
Posts: 1
1 Sep 2011 22:08:02 IST
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 100


New kid on the Block

Joined: 8 Sep 2011 14:11:07 IST
Posts: 1
8 Sep 2011 17:29:49 IST
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all the hundred

New kid on the Block

Joined: 8 Aug 2011 08:39:52 IST
Posts: 14
8 Sep 2011 18:51:04 IST
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answer is 10...the perfect squares as they have odd no of factors...

New kid on the Block

Joined: 8 Aug 2011 08:39:52 IST
Posts: 14
8 Sep 2011 18:51:54 IST
0 people liked this

answer is 10...all perfect squares have odd no of factors...so they get switched off and switched on..



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