Marching column – Street length from passage time A column of men 250 m long marches at 50 paces per minute, each pace being 75 cm. It takes 1 hour for the entire column to pass a street. What is the street length?

Introduction / Context:This problem mirrors train-platform logic. When an object of length L passes completely through a street (platform), the front must cover (street length + L). Converting pace rate to linear speed is essential.

Given Data / Assumptions:

• Column length L = 250 m.
• Rate = 50 paces/min, step length = 0.75 m.
• Total time to clear street = 60 min.

Concept / Approach:Total distance to clear = street + L. Linear speed s (m/min) = pace rate * step length. Use D = s * t, then street = D - L.

Step-by-Step Solution:

Verification / Alternative check:If the street is 2 km, then total to clear = 2250 m at 37.5 m/min, requiring 60 min, matching the statement.

Why Other Options Are Wrong:1 km, 1.5 km, 2.5 km: Do not satisfy D = s * t when adding L. Only 2 km yields the correct 60 min.

Common Pitfalls:Using 60 min to compute only street length; forgetting to add the column length; or mixing units of cm and m.

Final Answer:2 km