Two trains cross a pole in 4 sec and 6 sec respectively. Running in same direction in how much time will they take to cross each other if the ratio of their speed is 7 : 9.
Answer & explanation
Correct answer: option 2
Ratio of train 1 : train 2
Speed 7 : 9
Distance = Speed × Time
train 1 takes 4 sec to cross a pole ,
Length of train 1 = 4 × 7R = 28R
train 2 takes 6 sec to cross a pole ,
Similarly, legth of train 2 = 6× 9R = 54R
Total distance = 82R meter
As trains moves in same direction . so relative speed = (9 - 7 )R = 2R m/sec
Time taken by trains to cross each other = \(\frac{82R}{2R}\) = 41 sec.