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 Author: shreyasharma1206 [ 31 Jul 2020, 06:36 ] Post subject: Jack's watch gains 10 seconds every hour Jack's 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.360B. 720C. 1080D. 1440E. 2160

 Author: yashikaaggarwal [ 31 Jul 2020, 07:45 ] Post subject: Re: Jack's watch gains 10 seconds every hour 1 hour have 3600 secondJack's watch gains 10 seconds every hour. jack's watch will gain 1 hour or 3600 seconds in 3600/10 = 360 hoursthat means jack's watch will show 1 hour more than 10:00 am 15 days later (360/24 = 15 days)Also,Jose's watch loses 15 seconds every 30 minutes. or 30 seconds per hourjose's watch will lose 1 hour or 3600 seconds in 3600/30 = 120 hoursthat means jose's watch will show 1 hour less than 10:00 am 5 days later (120/24 = 5 days)or will show 3 hours less than 10:00 am 15 days later.hence Today set time = 10:00 am15 days later, (360 hours later)Jack's watch will show 11:00 AM and Jose's watch will show 7:00 AM= Total 360 hoursAnother 15 days later, (360 hours later) Jack's watch will show 12:00 PM and Jose's watch will show 4:00 AM= Total 720 hoursAnother 15 days later, (360 hours later)Jack's watch will show 13:00 PM and Jose's watch will show 1:00 AM= Total 1080 hoursAnother 15 days later, (360 hours later)Jack's watch will show 14:00 PM and Jose's watch will show 22:00PM= Total 1440 hoursAnother 15 days later, (360 hours later)Jack's watch will show 15:00 PM and Jose's watch will show 19:00PM= Total 1800 hoursAnother 15 days later, (360 hours later)Jack's watch will show 16:00 PM and Jose's watch will show 16:00PM= Total 2160 hoursSo shreyasharma1206, your question is ambiguous here because the clock needles does meet after 1080 hours but they are showing same time after 2160 hours. kindly rectify the part, what's been asked specifically

 Author: AndrewN [ 31 Jul 2020, 07:55 ] Post subject: Re: Jack's watch gains 10 seconds every hour yashikaaggarwal wrote:1 hour have 3600 secondJack's watch gains 10 seconds every hour. jack's watch will gain 1 hour or 3600 seconds in 3600/10 = 360 hoursthat means jack's watch will show 1 hour more than 10:00 am 15 days later (360/24 = 15 days)Also,Jose's watch loses 15 seconds every 30 minutes. or 30 seconds per hourjose's watch will lose 1 hour or 3600 seconds in 3600/30 = 120 hoursthat means jose's watch will show 1 hour less than 10:00 am 5 days later (120/24 = 5 days)or will show 3 hours less than 10:00 am 15 days later.hence Today set time = 10:00 am15 days later, (360 hours later)Jack's watch will show 11:00 AM and Jose's watch will show 7:00 AM= Total 360 hoursAnother 15 days later, (360 hours later) Jack's watch will show 12:00 PM and Jose's watch will show 4:00 AM= Total 720 hoursAnother 15 days later, (360 hours later)Jack's watch will show 13:00 PM and Jose's watch will show 1:00 AM= Total 1080 hoursAnother 15 days later, (360 hours later)Jack's watch will show 14:00 PM and Jose's watch will show 22:00PM= Total 1440 hoursAnother 15 days later, (360 hours later)Jack's watch will show 15:00 PM and Jose's watch will show 19:00PM= Total 1800 hoursAnother 15 days later, (360 hours later)Jack's watch will show 16:00 PM and Jose's watch will show 16:00PM= Total 2160 hoursSo shreyasharma1206, your question is ambiguous here because the clock needles does meet after 1080 hours but they are showing same time after 2160 hours. kindly rectify the part, what's been asked specificallyI think the point is that 1.00pm and 1.00am look identical on an analog watch, but I agree that the problem could more clearly convey such vital information: show the same time is indeed unclear, particularly in an age in which digital watches, which is not to even mention smart watches, are increasingly common.Thank you, in any case, yashikaaggarwal, for providing such a detailed response, and for sharing in the first place, shreyasharma1206.- Andrew

 Author: AnirudhaS [ 31 Jul 2020, 08:23 ] Post subject: Re: Jack's watch gains 10 seconds every hour When you say the "same time" it has to be the "same". One cannot be AM and the other PM!And for me the answer is undoubtedly 2160 hours, unless it is changed to "it looks the same"!

 Author: shreyasharma1206 [ 31 Jul 2020, 20:21 ] Post subject: Re: Jack's watch gains 10 seconds every hour Official answer provided by Experts Global is 1080 hoursPosted from my mobile device

 Author: GMATinsight [ 31 Jul 2020, 21:18 ] Post subject: Jack's watch gains 10 seconds every hour shreyasharma1206 wrote:Jack's 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.360B. 720C. 1080D. 1440E. 2160Jack's watch gains 10 seconds every hourJose's watch loses 15 seconds every 30 minutesi.e. Jose's watch loses 30 seconds every hourThe relative gap change between their watches = 10+30 = 40 seconds every hourTwo watches will show same time when gap between them is 12 hours40 seconds gap comes in 1 hourie. 12 hours gap will come in $$(\frac{1}{40})*(12*60*60) = 1080$$ hoursAnswer: Option CSubscribe to my YouTube Channel for FREE resource (1000+ Videos)Subscribe Topic-wise UN-bundled Video course. CHECK FREE Sample Videos

 Author: effatara [ 31 Jul 2020, 23:35 ] Post subject: Re: Jack's watch gains 10 seconds every hour Excellent solution, GMATinsight!I will try to make this conceptually easier to grasp. Imagine that the clock-face is a circular race track and the hour hands of the watches are two runners who start running clock-wise from the same point at the same time. The circumference of the track is, of course, 12 hrs (12*60*60 secs) where hours and seconds are, in this context, units of distance, not time. The Faster Hour Hand (FHH) moves 40 secs more than the Slower Hour Hand (SHH) in each hour. The FHH must come up from behind and catch up with the SHH for the two clocks to display the same time. To do this, FHH must make up for the length of the circumference of the track (12*60*60 secs). FHH gains 40 secs on SHH in 1 hr. FHH gains 1 second on SHH in 1/40 hrs. FHH gains 12*60*60 secs on SHH (catching up with it) in (12*60*60)/40 hrs = 1080 hrs

 Author: yashikaaggarwal [ 31 Jul 2020, 23:42 ] Post subject: Re: Jack's watch gains 10 seconds every hour So we are considering the time, the respective watches are showing irrespective of day/night 12 hour interval in between them?Posted from my mobile device

 Author: GMATinsight [ 01 Aug 2020, 00:46 ] Post subject: Re: Jack's watch gains 10 seconds every hour yashikaaggarwal wrote:So we are considering the time, the respective watches are showing irrespective of day/night 12 hour interval in between them?Posted from my mobile deviceTwo analog watches (usually used in questions of clocks unless mentioned otherwise) show the same time when they are 12 hours apart.

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