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# In a courtyard, one bell rings every 1/4 hour and another bell rings

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Current Student
Joined: 29 Dec 2016
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In a courtyard, one bell rings every 1/4 hour and another bell rings  [#permalink]

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20 Feb 2017, 09:33
5
00:00

Difficulty:

45% (medium)

Question Stats:

70% (01:58) correct 30% (01:56) wrong based on 125 sessions

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In a courtyard, one bell rings every 1/4 hour and another bell rings every 1/5 hour. Both bells ring together at exactly the beginning of each hour. Which of the following gives all the intervals that occur between any two rings of the bells in minutes ?

A. 6 and 9 only
B. 3, 6 and 9
C. 3, 12 and 15
D. 3, 6, 9 and 12
E. 3, 6, 10 and 12

Source: 4GMAT
Intern
Joined: 07 Apr 2015
Posts: 10
Re: In a courtyard, one bell rings every 1/4 hour and another bell rings  [#permalink]

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20 Feb 2017, 09:45
The bells ring at 12 minutes and 15 minutes. So they ring at 1) 12min/15min, 2) 24min/30min 3) 36min/45min 4) 48min/60min

The intervals between the listed times are: 3, 6, 9 and 12 mins.

Alternatively, we should notice that the the equation is linear and any interval of the ringing bells will be a constant-- in this instance "3" So C and E can be eliminated right away.
Marshall & McDonough Moderator
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Re: In a courtyard, one bell rings every 1/4 hour and another bell rings  [#permalink]

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20 Feb 2017, 09:57
skgmatclub2016 wrote:
In a courtyard, one bell rings every 1/4 hour and another bell rings every 1/5 hour. Both bells ring together at exactly the beginning of each hour. Which of the following gives all the intervals that occur between any two rings of the bells in minutes ?

A. 6 and 9 only
B. 3, 6 and 9
C. 3, 12 and 15
D. 3, 6, 9 and 12
E. 3, 6, 10 and 12

Source: 4GMAT

The question asks for the interval between any two rings of the bells. So, I feel D is not a fool proof answer.
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Re: In a courtyard, one bell rings every 1/4 hour and another bell rings  [#permalink]

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21 Feb 2017, 18:02
Need to find intervals occurred between any two rings. The bells ring at 12 minutes and 15 minutes. So the intervals are 3, 6, 9 and 12 mins.
Option D wins.
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Re: In a courtyard, one bell rings every 1/4 hour and another bell rings  [#permalink]

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16 Apr 2018, 17:13
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skgmatclub2016 wrote:
In a courtyard, one bell rings every 1/4 hour and another bell rings every 1/5 hour. Both bells ring together at exactly the beginning of each hour. Which of the following gives all the intervals that occur between any two rings of the bells in minutes ?

A. 6 and 9 only
B. 3, 6 and 9
C. 3, 12 and 15
D. 3, 6, 9 and 12
E. 3, 6, 10 and 12

For every 4th of an hour, bell one rings on minutes 15, 30, 45, and 60.

For every 5th of an hour, bell two rings on minutes 12, 24, 36, 48, and 60.

Since 15 - 12 = 3, 30 - 24 = 6, 45 - 36 = 9 and 60 - 48 = 12, the intervals are 3, 6, 9 and 12.

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In a courtyard, one bell rings every 1/4 hour and another bell rings  [#permalink]

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28 Nov 2018, 09:25
B1 = 1/4 H
B2 = 1/5 H
B1 & B2 at the beginning of every hour

Question = WOTF could be intervals of both

B1 = 0 ,15, 30, 45, 60/0
B2 = 0 , 12, 24, 36, 48, 60/0

0 to 12 = 12
12 to 15 = 3
15 to 24 = 9
24 to 30 = 6
30 to 36 = 6
36 to 45 = 9
45 to 48 = 3
48 to 60 = 12

leaves 3,6,9,12
In a courtyard, one bell rings every 1/4 hour and another bell rings   [#permalink] 28 Nov 2018, 09:25
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