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in Distance, Time and Speed by (238k points)
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A train moving at the rate of 72 kmph crosses a pole in 20 seconds. How much time will the tram require to cross car moving at speed of 18 kmph in opposite direction?
1. 20 s
2. 16 s
3. 10 s
4. 12 s

1 Answer

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Best answer
Correct Answer - Option 2 : 16 s

Given:

Speed of train = 72 kmph

Time = 20 seconds

Speed of car = 18 kmph

Formula used:

Speed = Distance / time

1 kmph = 5/18 m/s

Calculations:

Calculating length of train

⇒ 72 kmph = 72 × 5 / 18 m/s

⇒ Speed of train = 20 m/s

⇒ length of train = Speed × Time

⇒ length = 20 × 20

⇒ Length of train = 400 m

Now, calculate relative speed

⇒ car is moving in opposite direction as train hence relative speed = 72 + 18

⇒ Relative speed = 90 kmph

⇒ Relative speed = 25 m/s

⇒ Time taken to cross car = 400 / 25

⇒ Time taken = 16 sconds

Train takes 16 seconds to cross the car

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