A biker rides at 54 km/h and takes 4 minutes to fully cross a bridge. What is the length of the bridge in metres?

Introduction / Context:
Distance equals speed times time. When a point object crosses a fixed span at constant speed, the distance is simply the span length. Convert all units consistently to metres and seconds or km and hours.

Given Data / Assumptions:

• Speed = 54 km/h.
• Time = 4 minutes.
• Find bridge length in metres.

Concept / Approach:
Convert 54 km/h to m/s, multiply by time in seconds. Use 1 km = 1000 m and 1 h = 3600 s.

Step-by-Step Solution:

Verification / Alternative check:
Keeping units in km and h: speed = 54 km/h, time = 4/60 h = 1/15 h. Distance = 54 * (1/15) = 3.6 km = 3600 m. Matches.

Why Other Options Are Wrong:
2800, 3500, and 4500 m do not follow from the correct conversions. A small unit mistake often leads to these numbers.

Common Pitfalls:
Forgetting that 54 km/h equals 15 m/s or converting minutes to seconds incorrectly.

Final Answer:
3600 m