Multiple choice

The distance between two stations X and Y is 830 km. A train starts from X and runs towards Y at an average speed of S km/hr. Another train starts from Y and runs towards X, 30 minutes before the start of the train from X, at an average speed of (S + 20) km/hr. They cross each other in 3.5 hours from X. What is the value of S (in km/hr)?

  1. 90

  2. 120

  3. 100

  4. 80

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Train Y starts 0.5 hours earlier. In 3.5 hours, Train X travels 3.5S. In 4 hours, Train Y travels 4(S+20). Total distance = 3.5S + 4S + 80 = 830. 7.5S = 750, S = 100.

AI explanation

Train X travels for 3.5 hours, covering a distance of 3.5S km. Because train Y started 30 minutes earlier, it travels for 4 hours, covering 4(S + 20) km. Their combined distance equals the total separation of 830 km, so 3.5S + 4S + 80 = 830. Solving this linear equation yields 7.5S = 750, meaning S = 100. The result is 100.

Keep practicing — related questions