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?

Question

Solve this multiple-choice question and choose the correct option.

Curioustab · Accepted Answer

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: tA = 100 / 1.3889 ≈ 72 stB = tA + 8 = 80 svB = 92 / 80 = 1.15 m/s ⇒ 1.15 * 3.6 = 4.14 km/h 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

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?

Answer

Explanation