Multiple choice

A train takes 18 sec to cross a station which is 162 m long and takes 15 sec to cross another station which is 120 m long. The length of the train is

  1. 70 m

  2. 80 m

  3. 90 m

  4. 100 m

  5. 120 m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let L be the length of the train and v be its speed. (L + 162) / 18 = v and (L + 120) / 15 = v. So, (L + 162) / 18 = (L + 120) / 15. 15(L + 162) = 18(L + 120). 15L + 2430 = 18L + 2160. 3L = 270, so L = 90.

AI explanation

Let L be the length of the train and v be its speed. For the first station, L plus 162 equals v times 18, and for the second station, L plus 120 equals v times 15. Subtracting the second equation from the first gives 42 equals 3v, so the speed v is 14 m/s. Substituting 14 back into the second equation gives L plus 120 equals 210, so L equals 90 meters. The result is 90 m.

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