Question

A train leaves a point A at 5 pm and reach another point B at 11 pm. Another train leaves point B at 7 pm and reach point A at 10 pm. At what point will the two trains meet?

Answer 1

Answer: I think the two trains meet at 9pm

Explanation: A=train a B=train b

If A is traveling for 6 hours and B is traveling for 3 hours, then you minus 3 hours from A, so you are left with 3 hours. Convert that into time, and you are left with 9pm!

Hope this helps! :)

Answer 2

Step-by-step explanation:

let's think this through.

train a goes from A to B in 6 hours. that means with a speed of 1/6 / hour.

train b goes from B to A in 3 hours, so it is twice as fast as train a = 2/6 / hour.

when train b leaves B (at 7pm), train a was already traveling for 2 hours (1/3 of the whole trip) leaving it with 4 hours to go (2/3 if the distance).

that means that at that point now both trains are moving against each other with a relative speed of 3 times the

speed of a (the original speed of a plus the double speed of b).

this is the same as one train standing, and the other going the whole distance with 3 times the speed of a.

the whole distance is 2/3 of AB.

the speed is 3/6 / hour = 1/2 / hour.

so, a single train with that speed would cover the total distance AB in 2 hours. or half of the distance in 1 hour.

the question now, how long for 2/3 of AB.

the distances relate by a factor :

1/2 × f = 2/3

f = 2/3 / 1/2 = 2/3 × 2/1 = 4/3

now we need to multiply also the time in the distance/time speed ratio by this factor.

therefore, 2/3 of the total distance is done in 1×4/3 = 4/3 of an hour.

that means both trains meet after 4/3 of an hour after 7pm.

that is 7pm plus 1 hour and 20 minutes giving us 8:20pm.