Question

A railway passenger counts the telegraph posts on the line as he passes them while travelling if the poles are 50 m apart and the train is going at the speed of 48 km/hr. How many posts will be passed by the train per minute?
A. 15
B. 16
C. 18
D. 20

Answer 1

Hint: Convert the speed of the train in m/ minutes by the formula-
$S(m/\min ) = \dfrac{{S(km/hr) \times 1000m}}{{60\min }}$ and then solve the question.

Complete Step-by-Step solution:
We have been given that the poles are 50 m apart and the train is going at the speed of 48 km/hr.
Now, speed of train in m/min is given by-
$S(m/\min ) = \dfrac{{S(km/hr) \times 1000m}}{{60\min }}$
Put the value of speed in km/hr as 48 km/hr.
$S(m/\min ) = \dfrac{{48 \times 1000m}}{{60\min }} = 800m/\min $
Therefore, in 1 min the train crosses 800 m.
If the poles are 50 m apart then the number of poles in 800 m stretch $ = \dfrac{{800}}{{50}} = 16$poles.
Hence, the correct option is C. 16 poles.

Note: Whenever such types of questions appear then write down the given information in the question. Then use the formula to convert the speed into m/min and then using the basic formulas to find the number of poles.