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Question

Two trains start from places A and B. respectively, and travel towards each other at the speeds of 60 km/h and 50 km/h. respectively. By the time they meet, the faster train has travelled 110 km more than the slower train. What is the distance between A and B?

The correct answer is

1210 Km

Understanding the Train Meeting Problem

This problem involves two trains traveling towards each other from different locations, A and B, at different speeds. We are given their speeds and the difference in the distance they cover until they meet. Our goal is to find the total distance between A and B.

Analyzing the Given Information

  • Speed of the faster train (starting from A, let's assume) = 60 km/h.
  • Speed of the slower train (starting from B) = 50 km/h.
  • The faster train travels 110 km more than the slower train by the time they meet.
  • They start at the same time and travel for the same duration until they meet.

Setting up the Equations

Let \(t\) be the time in hours until the two trains meet. Since they start simultaneously and travel towards each other until they meet, the time taken by both trains will be the same.

  • Distance covered by the faster train = Speed \(\times\) Time = \(60t\) km.
  • Distance covered by the slower train = Speed \(\times\) Time = \(50t\) km.

We are told that the faster train travels 110 km more than the slower train. We can write this as an equation:

Distance covered by faster train - Distance covered by slower train = 110 km

\(60t - 50t = 110\)

Solving for Time Taken to Meet

Now, let's solve the equation for \(t\):

\( (60 - 50)t = 110 \)

\( 10t = 110 \)

\( t = \frac{110}{10} \)

\( t = 11 \) hours

So, the trains meet after 11 hours.

Calculating the Distances Covered by Each Train

Now that we know the time \(t = 11\) hours, we can calculate the distance covered by each train:

  • Distance covered by faster train = \(60 \times 11 = 660\) km.
  • Distance covered by slower train = \(50 \times 11 = 550\) km.

Finding the Total Distance Between A and B

When the two trains meet, the sum of the distances they have covered is equal to the total distance between A and B.

Total distance = Distance covered by faster train + Distance covered by slower train

Total distance = \(660 \text{ km} + 550 \text{ km}\)

Total distance = \(1210 \text{ km}\)

Let's verify the difference in distance: \(660 \text{ km} - 550 \text{ km} = 110 \text{ km}\), which matches the information given in the problem.

Therefore, the distance between A and B is 1210 km.

Revision Table: Key Concepts

Concept Explanation
Speed Rate of change of distance over time. (Distance/Time)
Distance Speed × Time
Time Distance / Speed
Meeting Time (Travelling Towards Each Other) If starting at the same time, both travel for the same duration until they meet.
Total Distance (Meeting Towards Each Other) Sum of distances covered by each object.
Difference in Distance Covered (Speed of Faster × Time) - (Speed of Slower × Time) = (Speed of Faster - Speed of Slower) × Time

Additional Information: Relative Speed Concept

While we solved this problem using the difference in distances, it can also be conceptualized using relative speed. When two objects move towards each other, their relative speed is the sum of their individual speeds. The relative speed tells us how quickly the distance between them is decreasing.

  • Relative speed = Speed of train A + Speed of train B
  • Relative speed = \(60 \text{ km/h} + 50 \text{ km/h} = 110 \text{ km/h}\).

The difference in distance covered (110 km) is because the faster train travels for 11 hours, and in each hour, it covers \(60 - 50 = 10\) km more than the slower train. Over 11 hours, this difference accumulates to \(10 \times 11 = 110\) km.

The total distance can also be found by calculating the time it takes for the 110 km "gap" created by the speed difference to result in a 110 km lead for the faster train. This time is \(110 \text{ km} / 10 \text{ km/h} = 11\) hours. Then, multiply this time by the relative speed to get the total distance: \(110 \text{ km/h} \times 11 \text{ hours} = 1210 \text{ km}\).

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Important Questions from Relative Speed

  1. A train can cross a tunnel of length 600 m in 54 seconds, and it can cross a 350 m long bridge in 36 seconds. Which of the following statements is/are correct?

    (i) The speed of the train is 60 km/h.

    (ii) The length of the train is 150 m

  2. Raghu and Raman start together to walk a certain equal distance at a speed of 10 km/h and 8 km/h, respectively. Raghu arrives 30 minutes before Raman arrives. Find the distance between the start and the end point. 

  3. A and B started simultaneously and proceeded towards each other from places X and Y, respectively. After meeting each other at a certain point on the way, A and B took 3.2 hours and 1.8 hours, to reach Y and X, respectively. If the speed of B was 12 km/h, then the speed (in km/h) of A was:

  4. Anil started his journey in the morning. Till 10 a.m., he covered \(\frac{1}{2}\) of his journey, and on the same day till 1 a.m., he covered \(\frac{4}{5}\) of his journey. At what time did he start his journey?

  5. Munaf and Surya start simultaneously at the same point on a circular track and run along the track in the same direction. The point on the track at which they meet for the 31st time is the same as that at which they meet for the 43rd time. If the ratio of the speed of the faster boy to that of the slower one is n ∶ 1, where ‘n’ is a natural number, which of the following is NOT a possible value of ‘n’?

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