rohitgoel15
Train A leaves New York for Boston at 3 PM and travels at the constant speed of 100 mph. An hour later, it passes Train B, which is making the trip from Boston to New York at a constant speed. If Train B left Boston at 3:50 PM and if the combined travel time of the two trains is 2 hours, what time did Train B arrive in New York?
(1) Train B arrived in New York before Train A arrived in Boston.
(2) The distance between New York and Boston is greater than 140 miles.
Please help me know the difficulty level of this question. I was not able to solve it in even 5 mins

in this kind of question, it would be better if we picture its concept by drawing lines that explain both the time train A & B need to get Boston & New York and the distance between Boston & New York
train A
New York ----------1hr, 100miles----------------**(4:00pm)------x hr, 100x miles------>>
Boston speed: 100 miles/ 1hr
3:00pm set out from New York to Boston
train B
New York <<----100/y hr, 100 miles-----------**(4:00pm)------1/6 hr, y/6 miles---------
Boston speed: y miles/ 1hr
3:50pm set out from Boston to New York
here we assume that the speed of train B is y miles/ 1hr, and, after the two trains pass each other in 4:00pm, train A travels another x hr to reach to the destination Boston, and from the statement given in the question
we know that, since the total travel time of the two trains is 2 hr, there comes the equation of( 1 + x + 100/y + 1/6 = 2 ), also the distance of train A still need to travel through to get to New York after two trains passed each other is 100x miles, this will equal to the distance of train B have already traveled before two trains passed each other, thus comes another equation( 100x = y/6 ), two unknown and two equations so we could solve this unknown of x = 1/2 or 1/3 and y = 300 or 200, with my logic of solving illustatrate as below
1 + x + 100/y + 1/6 = 2 ......(1)
100x = y/6 ......(2)
arrange the numbers in (1) to the left side we get x + 100/y = 5/6 .....(3)and multiply by 6 to equation (2) to cancel the denomiator we get y = 600x ....(4), take the unknown y in equation(4) to (3) we get x + 100/600x =5/6, multiply two sides by x it becomes x^2 + 1/6 = 5/6x, so its (x-2)(x-3)=0, thus there comes two scenarios x = 1/2 or 1/3 and y = 300 or 200
SCENARIO(1)
if Vb = y =200, the distance from New York to Boston is 133.3 miles,
train A spends 1 1/3hr to reach Boston while train B spends 100/200 + 1/6 = 4/6hr to reach New York
SCENRIO(2)
if Vb = y =300, the distance from New York to Boston is 150 miles,
train A spends 1 1/2hr to reach Boston while train B spends 100/300 + 1/6 = 3/6hr to reach New York
here we go back to the question, in proposition (1) it says train B travel faster than train A, thus only scenario (2) fits, sufficient to get us to the answer, and in proposition (2) it requires that the distance they travel will be more than 140 miles, it is also only scenario (2) fits, sufficient