Math Problem Statement

Two trains 130 m and 110 m in lengths move in the same direction at the same time. The faster train completely overtakes the slower train in 15 seconds. If the slower train moves at half of its speed, the overtaking would take 10 seconds. Find the speed of the two trains.

Solution

Let the speed of the faster train be xx m/s and the speed of the slower train be yy m/s.

Step 1: Form the First Equation

The total distance to be covered for overtaking is the sum of the lengths of the two trains:
130+110=240 m130 + 110 = 240 \text{ m}
Since they are moving in the same direction, their relative speed is:
(xy) m/s(x - y) \text{ m/s}
The time taken to overtake is 15 seconds, so we set up the equation:
240xy=15\frac{240}{x - y} = 15
xy=24015=16x - y = \frac{240}{15} = 16

Step 2: Form the Second Equation

When the slower train moves at half its speed, its new speed is y2\frac{y}{2}.
The new relative speed is:
xy2x - \frac{y}{2}
The time taken for overtaking in this case is 10 seconds:
240xy2=10\frac{240}{x - \frac{y}{2}} = 10
xy2=24010=24x - \frac{y}{2} = \frac{240}{10} = 24

Step 3: Solve for xx and yy

We now have the system of equations:

  1. xy=16x - y = 16
  2. xy2=24x - \frac{y}{2} = 24

Solve for yy:

Rewriting the second equation:
x=24+y2x = 24 + \frac{y}{2}
Substituting x=y+16x = y + 16 into this equation:
y+16=24+y2y + 16 = 24 + \frac{y}{2}
Multiply everything by 2 to eliminate the fraction:
2y+32=48+y2y + 32 = 48 + y
2yy=48322y - y = 48 - 32
y=16y = 16

Solve for xx:

x=16+16=32x = 16 + 16 = 32

Final Answer:

  • Speed of the faster train: 32 m/s
  • Speed of the slower train: 16 m/s

Would you like a step-by-step verification?

Here are 5 related questions to explore further:

  1. What would be the time taken for the faster train to overtake the slower train if they were moving in opposite directions?
  2. How would the overtaking time change if the lengths of the trains were different?
  3. What would be the speed of the slower train if the overtaking time was 20 seconds instead of 15?
  4. How does the concept of relative speed apply to other real-life scenarios like river currents and airplane wind resistance?
  5. If the trains were accelerating instead of moving at constant speeds, how would the calculation change?

Tip: Always remember that in problems involving relative motion in the same direction, subtract the speeds; in opposite directions, add them. 🚆

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Math Problem Analysis

Mathematical Concepts

Relative Speed
Algebra
Linear Equations

Formulas

Distance = Speed × Time
Relative Speed = (Speed of first object) - (Speed of second object)

Theorems

Relative motion in the same direction

Suitable Grade Level

Grades 9-11