Supposing that the telegraph poles on a railroad are 50 m apart, how many poles will be passed by a train in 4 h if the speed of the train is 45 km/h?

(Include both the poles at the starting point as well as the one at the end of the journey in your count)

Correct option is D

Given:

Distance between two telegraph poles = 50 m

Speed of the train = 45 km/h

Time of travel = 4 hours

We are asked to find the total number of telegraph poles the train will pass in 4 hours, including both the poles at the starting point and the one at the end of the journey.

Formula Used:

Distance traveled by the train = Speed × Time

Number of poles passed =$$\frac{\text{Distance traveled}}{\text{Distance between two poles}} + 1$$​ (to include the starting and ending poles)

Solution:
The speed is given in km/h, but the distance between poles is in meters, so we first convert the speed into meters per hour:

​$$45 \, \text{km/h} = 45 \times 1000 = 45000 \, \text{m/h}$$​
The total distance traveled by the train in 4 hours is:

Distance =$$\text{Speed} \times \text{Time} = 45000 \, \text{m/h} \times 4 \, \text{h} = 180000 \, \text{m}$$​
Since the distance between two poles is 50 meters, the number of poles passed (including the starting and ending poles) is:

Number of poles =$$\frac{\text{Total distance}}{\text{Distance between poles}} + 1 = \frac{180000}{50} + 1 = 3600 + 1 = 3601$$​

The train will pass 3601 poles in 4 hours.