Ratio of length of two trains is 4 : 5. Coming from opposite direction, they cross a pole in 4 seconds each . Then in what time will they cross each other .
Answer & explanation
Correct answer: option 3
Ratio of train 1 : train 2
Distance 4 : 5
Speed 4 : 5 ( distance = speed × time , so ratio of distance and speed is same .)
As both train cross a man in 4 sec . So length of train1
Distance = Speed × Time
Length of train 1 = 4R × 4 = 16R
Similarly, legth of train 2 = 5R × 54 = 20R
Total distance = 36R meter
As trains moves in opposite direction . so relative speed = ( 4 + 5 )R = 9R m/sec
Time taken by trains to cross each other = \(\frac{36R}{9R}\) = 4 sec .