Aptitude Discussion

Q. |
Two stations $A$ and $B$ are 110 km apart on a straight line. One train starts from $A$ at 7 am and travel towards $B$ at 20 km/hr speed. Another train starts from $B$ at 8 am and travel towards $A$ at 25 km/hr speed. At what time will they meet? |

✖ A. |
9 am |

✔ B. |
10 am |

✖ C. |
11 am |

✖ D. |
None of these |

**Solution:**

Option(**B**) is correct

In 1 hour (7 am to 8 am) tarin from station A travels 20 km distance and reaches to $C$, (say).

$A$ ----------------- $C$ ---------------$B$

7 am --------------------------------- 8 am

$AC$ = 20 km, $CB$ = 90 km

Distance travelled in 1 hour = 20 km

Remaining distance =$110−20$ = 90 km

\(\text{Time}=\dfrac{\text{Distance}}{\text{Speed}}\)

\(\dfrac{90}{20+25}=2\) hours

So, time = 8 am + 2 am = **10 am**

**Imran**

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Hey Imran, time is added AFTER $A$ has traveled for 1 hour (i.e. time is 8 AM now). Now it takes two more hours after 8 AM when both $A$ and $B$ travel at the speed of 20 km/hr and 25 km/hr respectively.

That is why 2 hours time is added after 8 AM and not 7 AM, it has nothing to do with the first or second train's time.

Hope that helps :)

thanks shireen..i got it..

**Madhu**

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Thank you, Aman, now I got it

Pleasure is all mine, Madhu :)

**Madhu**

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how do we get AC =20

Train from station $B$ starts AFTER 1 hour (at 8 am). So in that time, train from station $A$ travels till point $C$ for 1 hour, with the speed of 20 km/hr. Which makes distance $AC=20$ km.

Hope this helps.

Why do we add $2$ hours with that of second train's starting time?

Are we not supposed to add with the firsts'?