A train of length 245 metres takes 20 seconds to cross a 355 metres long bridge. How much time (in seconds) will the train take to cross a 390 metres long platform?
- A6.5
- B9
- C21.16
- D15
Solution & Step-by-step Explanation
When a train crosses a bridge, the total distance covered is the sum of the length of the train and the length of the bridge.
Total Distance
1
=245+355=600metres
Time
1
=20seconds
Speed of the train=
Time
1
Distance
1
=
20
600
=30m/s
Now, to cross a 390 metres long platform, the total distance covered will be:
Total Distance
2
=245+390=635metres
Time taken=
Speed
Distance
2
=
30
635
≈21.16seconds
Total Distance
1
=245+355=600metres
Time
1
=20seconds
Speed of the train=
Time
1
Distance
1
=
20
600
=30m/s
Now, to cross a 390 metres long platform, the total distance covered will be:
Total Distance
2
=245+390=635metres
Time taken=
Speed
Distance
2
=
30
635
≈21.16seconds