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# Clock

Author Message
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Intern
Joined: 25 Oct 2010
Posts: 46
WE 1: 3 yrs
Followers: 0

Kudos [?]: 21 [0], given: 13

Clock [#permalink]  02 Nov 2010, 23:29
00:00

Difficulty:

(N/A)

Question Stats:

75% (01:25) correct 25% (01:28) wrong based on 4 sessions
A certain clock marks every hour by striking a number of times equal to the hour,and the time required for a stroke is exactly equal to the time interval between strokes. At 6:00 the time lapse between the beginning of the first stroke and the end of the last stroke is 22 seconds. at 12:00 ,how many seconds elapse between the beginning of the first stroke and the end of the last stroke?

A.72
B.50
C.48
D.46
E.44
[Reveal] Spoiler: OA
Ms. Big Fat Panda
Status: Biting Nails Into Oblivion
Joined: 09 Jun 2010
Posts: 1855
Followers: 340

Kudos [?]: 1390 [1] , given: 194

Re: Clock [#permalink]  02 Nov 2010, 23:33
1
KUDOS
At 6:00 it'll chime 6 times. If we assume that the time taken to chime is x, then time between chimes is also x. So you have 6 chimes, which is 6x and 5 time intervals between chimes. This means that 11x = 22 seconds. Thus x = 2 seconds.

By a similar logic, at 12:00, there are 12 chimes and 11 intervals so the total time is (12+11)x = 23x = 46 seconds.

Posted from GMAT ToolKit
Retired Moderator
Joined: 02 Sep 2010
Posts: 807
Location: London
Followers: 76

Kudos [?]: 474 [0], given: 25

Re: Clock [#permalink]  02 Nov 2010, 23:40
student26 wrote:
A certain clock marks every hour by striking a number of times equal to the hour,and the time required for a stroke is exactly equal to the time interval between strokes. At 6:00 the time lapse between the beginning of the first stroke and the end of the last stroke is 22 seconds. at 12:00 ,how many seconds elapse between the beginning of the first stroke and the end of the last stroke?

A.72
B.50
C.48
D.46
E.44

At 6:00, there are 6 strokes :
Strke<-->Strke<-->Strke<-->Strke<-->Strke<-->Strke
This last 22 seconds
There 6 strokes and 5 intervals, each of which lasts 2 seconds (22/11)

At 12:00 :
Strke<-->Strke<-->Strke<-->Strke<-->Strke<-->Strke<-->Strke<-->Strke<-->Strke<-->Strke<-->Strke<-->Strke

Which is exactly 2x(time taken for 6:00)+1 extra interval
This 2x22+2 = 46 seconds

_________________
Manager
Joined: 01 Nov 2010
Posts: 183
Location: Zürich, Switzerland
Followers: 2

Kudos [?]: 15 [0], given: 20

Re: Clock [#permalink]  09 Nov 2010, 05:52
Notice 2 things-
1. stroke time == interval time
2. Beginning of first stroke to end of last stroke indicates 1 interval time lesser than number of strokes.

For 6 'o clock--> strokes =6 and intervals=5, which take 22 seconds i.e. 2 sec per stroke/interval
for 12 'o clock-> strokes=12 and intervals=11, total 23 so the time interval=46

Re: Clock   [#permalink] 09 Nov 2010, 05:52
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