GMAT Problem Solving (PS) | Re: Train A is traveling at 40 miles per hour and Train B is traveling on

Without formulas and using some approximation

In 1 hr train A would have travelled 15+40=55 miles
In 1 hr train B would have travelled 60 miles. This means train B passes train A before hitting 60 minutes.
The only answer less than 60 is A

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