Multiple choice

A train passes a telegraph post in $8$ seconds and a $264$ m long bridge in $20$ seconds. What is the length of the train?

  1. $170$ m
  2. $176$ m
  3. $164$ m
  4. $158$ m
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let L be the length of the train and v be its speed. L = v * 8. Also, L + 264 = v * 20. Substituting L = 8v into the second equation: 8v + 264 = 20v, so 12v = 264, v = 22 m/s. Then L = 22 * 8 = 176 m.

AI explanation

Let the length of the train be L meters, which means its speed is L/8 meters per second since it passes a post in 8 seconds. When passing a 264 m bridge in 20 seconds, the total distance covered is L plus 264, giving the equation L plus 264 equals 20 times the speed, or L plus 264 equals 20 times L/8. Solving the equation L plus 264 equals 2.5 times L gives a train length of 176 meters.

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