rohan2345 wrote:
Jacks watch gains 10 seconds every hour. Jose’s watch loses 15 seconds every 30 minutes. If they set their watches correctly at 10:00 am, after how many hours will the two watches show the same time again?
A- 360 hours
B- 720 hours
C- 1080 hours
D- 1440 hours
E- 2160 hours
Jacks watch GAINS 10 seconds every HOUR. Jose’s watch loses 15 seconds every 30 minutesThis means Jose’s watch LOSES 30 seconds every HOUR
In
1 HOUR, the time difference between the two watches is
40 seconds
So, in
2 HOURS, the time difference between the two watches is
80 seconds
So, in
3 HOURS, the time difference between the two watches is
120 seconds
Or we can say:, in
3 HOURS, the time difference between the two watches is
2 MINUTES
So, in
90 HOURS, the time difference between the two watches is
60 MINUTES
In other words, in
90 HOURS, the time difference between the two watches is
1 HOUR
KEY CONCEPT: In order for their watches to show the same time, we need a time difference of
24 HOURS
We know that, in
90 HOURS, the time difference between the two watches is
1 HOUR
Multiple both values by 24 to get: in
2160 HOURS, the time difference between the two watches is
24 HOURS
Answer: E
Cheers,
Brent
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