Question

(b) 25
3) A train 450 m long, crosses a pole in 22-s.
1
2
What is the speed of the train in km/h?
(a) 70
(b) 72
(c) 69
(d) 60
​

Answer 1

Explanation:

A train 450 m long crosses a pole in 22*1/2 seconds. What is the speed of the train in km/h?

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450m ÷ 22.5 s = 20m per s

Speed = 20 m/s

1000m = 1km

60s = 1 minute(min)

60min = 1 hour (h)

1 h = 3600s

Solution:

Speed = 20 m /s:

20 m × 3600s = 72000 m

1s × 3600s = 3600 s

Speed = 72000 m/3600s

Since 1km = 1000m, we have to

72000÷1000= 72km

3600s= 1h

Speed = km/h

Speed = 72km/h

Answer 2

Answer:

b) 72 km/hr

Explanation:

Length of the Train(d) = 450 m

Time taken to cross the pole (t) = 22 s

Speed = Distance

Time

= 450/22

= 225/11 m s^-1

= 225 x 18

11 5

= 45 x 18

11

= 810/11

= 73.63 km/hr

= 72 km/hr (approx)

A Helpful Tip:

To Convert km/hr to m/s:

1 km/h = 1 km

1 hr

= 1000 m (Since 1 km = 1000 m)

3600 s (Since 1 hr = 3600 s)

= 10/36

= 5/18

Hence, to convert km/h to m/s you need to multiply the given values by 5/18.

To Convert km/h to m/s:

You need to multiply the given values by 18/5 i.e. the reciprocal of 5/18.