Question 348503
train A 100mph
train B = 110 mph
...
train A 1210
train B 1222
difference = 12 minutes.
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in 12 minutes train A has traveled (12/60) * 100= 20 miles
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Difference between their speeds = 10 mph.
train B catches up 10 miles every 1 hour
it has to catch up 20 miles
Time = distance / speed 
time 20/10
= 2hours.
Train B will catch up at 0222 hours