Two train having equal length cross a pole in 7 sec and 9 sec respectively . Running in opposite direction in what time will they cross each other ?
Answer & explanation
Correct answer: option 2
Ratio of train 1 : train 2
Time 7 : 9
Speed 9 : 7 ( distance = speed × time , so ratio of time and speed is inverse .)
Distance = Speed × Time
Length of train 1 = 9R × 7 = 63R
Similarly, legth of train 2 = 7 × 9R = 63R
Total distance = 126R meter
As trains moves in opposite direction . so relative speed = ( 7 + 9 )R = 16R m/sec
Time taken by trains to cross each other = \(\frac{126R}{16R}\) = 7\(\frac{7}{8}\) sec.