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Joined: 02 Sep 2009
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Six bells commence tolling together and toll at intervals of 2, 4, 6,
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07 Aug 2019, 00:40
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27% (01:18) correct 73% (01:46) wrong based on 64 sessions
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Six bells commence tolling together and toll at intervals of 2, 4, 6, 8 10 and 12 seconds respectively. In 30 minutes, how many times do they toll together ? A. 10 B. 12 C. 15 D. 16 E. 4
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Re: Six bells commence tolling together and toll at intervals of 2, 4, 6,
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07 Aug 2019, 00:47
The bells will toll together when there is one time interval which is divided by every single time interval. Thus, we need to find the LCM of 2,4,6,8,10,12 LCM : 120
Thus, in 30 minutes = 30 * 60 seconds, they will toll together:
\(\frac{30*60}{120}\) = 15
IMO the answer is C.
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Six bells commence tolling together and toll at intervals of 2, 4, 6,
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07 Aug 2019, 02:28
We need to find the LCM of the intervals at which the bells toll, i.e. 2,4,6,8,10,12 Prime factorization for the intervals are: 2=2; 4=2^2; 6=2x3; 8=2^3; 10=2x5; 12=2^2 x 3 Hence LCM=2^3 x 3 x 5 = 120. Number of times the bells toll together = 1+(30x60)/120 = 1+15 = 16. You need to add one because the question stem says they commence tolling together. Meaning at time 0, they all tolled once.
The answer is therefore D.
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Re: Six bells commence tolling together and toll at intervals of 2, 4, 6,
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07 Aug 2019, 04:02
the all bells rang once at zeroth second next they will ring together at the LCM (all the fgiven individual times ) =120 second= 2mins
total interval 30 mins number of times in 0 to 30 = 1+30/2 =16 times we need to count the first ringing



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Re: Six bells commence tolling together and toll at intervals of 2, 4, 6,
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08 Aug 2019, 11:21
Bunuel wrote: Six bells commence tolling together and toll at intervals of 2, 4, 6, 8 10 and 12 seconds respectively. In 30 minutes, how many times do they toll together ?
A. 10 B. 12 C. 15 D. 16 E. 4 total time = 30*60 ; 1800 sec LCM for 2, 4, 6, 8 10 and 12 ; 120 so bells will toll together interval 120 sec 1800/120 ; 15 times + 1 since they have tolled together at 0 sec IMO D ; 16



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Re: Six bells commence tolling together and toll at intervals of 2, 4, 6,
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12 Aug 2019, 11:54
Bunuel wrote: Six bells commence tolling together and toll at intervals of 2, 4, 6, 8 10 and 12 seconds respectively. In 30 minutes, how many times do they toll together ?
A. 10 B. 12 C. 15 D. 16 E. 4 The least common multiple (LCM) of 2, 4, 6, 8, 10, and 12 is 120. Thus, the bells toll together every 120 seconds (or 2 minutes), so in 30 minutes they will toll simultaneously 30/2 = 15 times. However, since they commence tolling together at the beginning (i.e., they are tolling together at the 0th second or the 0th minute), we need to add 1 to 15 and thus they toll together a total of 16 times. Answer: D
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Re: Six bells commence tolling together and toll at intervals of 2, 4, 6,
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12 Aug 2019, 11:54






