Two trains cross a pole in 4 sec and 5 sec respectively. Running in same direction in how much time will they take to cross each other if the ratio of their speed is 5 : 7.
Answer & explanation
Correct answer: option 2
Ratio of train 1 : train 2
Speed 5 : 7
Distance = Speed × Time
train 1 takes 4 sec to cross a pole ,
Length of train 1 = 4 × 5R = 20R
train 2 takes 5 sec to cross a pole ,
Similarly, legth of train 2 = 5× 7R = 35R
Total distance = 55R meter
As trains moves in same direction . so relative speed = (7 - 5 )R = 2R m/sec
Time taken by trains to cross each other = \(\frac{55R}{2R}\) = 27.5 sec.