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 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
In some regards, this is more of a Reading Comprehension question than a Quantitative question.
... the time required FOR a stroke is exactly equal to the time interval BETWEEN strokes.
So, we have moments of silence and moments where the clock is ringing. Each period of silence is the
same duration as each period of noise.
So, for example, at 3:00, we have (
RING)(
silence)(
RING)(
silence)(
RING)
At 6:00 the time lapse between the beginning of the first stoke and the end of the last stroke is 22 seconds
So, at 6:00, we have (
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)
Notice that, if we count
RINGS and
silences, we have a total of 11 periods.
If the entire event takes 22 seconds, we can conclude that
each period is 2 seconds long.
At 12:00, how many seconds elapse between the beginning of the first stroke and the end of the last stroke?
We can conclude that this event will include 12
RINGS and 11
silences for a total of 23 periods.
Since each each period is
2 seconds long, the entire event will take
46 seconds
Answer:
D
Aside: If you're not convinced that there will be 12
RINGS and 11
silences, you can always write it out . ..
At 12:00, we have (
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)(
silence)(
RING)
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
