Jack's way h gains 10 secs and Jose's loses 15 sec in 30 min or 30 secs in 1 HR..
So the difference in 1 HR is 40 secs..

Now since it is given 10:00 am and asks for the same time again, it means a difference of 24 hrs since we are taking AM in consideration otherwise it would have been 12 hrs..

So if 40sec in 1hr, 24 hour in 24*60*60/40=2160 hrs
Had it been 10:00 to 10:00 that is 12 hrs ana will be 2160/2=1080

But as per the wordings of question Ans should be 2160..
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


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