gmatapril wrote:anshumishra wrote:gmatapril wrote:A certain clock marks every hour by striking a number of times equal to the hour, and the time require for a stroke is exactly equal to the time interval between strokes. At 6:00 the time lapse between the beginning of the first stoke 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
Answer is D
I am unable to understand the question.
Here is how I represent the time period for 6 O'clock :
x - x - x - x - x - x
x -> represents strokes (A total of 6)
- -> represents time interval between strokes (A total of 5)
Since the time taken for the strokes and the time interval between the strokes are same, say "t"
t = 22/(6+5) = 2 sec
So, at 12 O'clock we will have 12strokes (x) and 11 times intervals between strokes (-)
x - x - x - x - x - x - x - x - x - x - x - x
So, total time = (12+11)*t = 23*2 = 46
d
i am sorry i have a very sill question but can you please explain why did you add(6+5)
No problem. Let me try to explain it using the example I mentioned above :
x - x - x - x - x - x
x -> represents strokes (A total of 6)
- -> represents time interval between strokes (A total of 5)
Now, as per the question each stroke (i.e. x) and the time interval b/w the strokes (i.e. "-") takes equal unit of time, say "t".
So, 6 strokes take a total of
6t time
5 intervals between the strokes take
5t time
Now checkout the part of the question :
At 6:00 the time lapse between the beginning of the first stoke and the end of the last stroke is 22 seconds.
This time interval (22 seconds) is the same which we have calculated above (6 strokes as it was 6:00, and 5 intervals between the strokes as explained above)
=> 6t+5t = 22
=> 11t = 22
=> t = 22/11 = 2.
Hope that clears your doubt.
