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

_________________

Test confidently with gmatprepnow.com