100 m race with start and time gap: A and B run a 100 m race. A runs at 5 km/h, gives B an 8 m start, and still beats B by 8 s. What is B’s speed?

Introduction / Context:
We know A's speed and the time gap at finish. Using the 8 m start, we compute B's required time and hence B's speed.

Given Data / Assumptions:

• A's speed = 5 km/h = 5000/3600 = 1.3889 m/s.
• Race length 100 m for A; B starts 8 m ahead → B needs 92 m.
• A finishes 8 s before B.

Concept / Approach:
Compute A's finish time; add 8 s to get B's finish time for 92 m; then speed = distance/time.

Step-by-Step Solution:

Verification / Alternative check:
Using exact fractions yields the same 4.14 km/h (to two decimals).

Why Other Options Are Wrong:
Other values correspond to incorrect conversion or ignoring the 8 m start.

Common Pitfalls:
Converting km/h to m/s incorrectly; misreading the start distance as time advantage.

Final Answer:
4.14 km/h