You travel three equal legs of 39 km each at 26 km/h, 39 km/h, and 52 km/h, respectively. What is your average speed for the entire journey?

Introduction / Context:
For equal distances traveled at different speeds, the average speed is not the arithmetic mean. It is computed via total distance divided by total time, effectively a harmonic-mean aggregate across segments.

Given Data / Assumptions:

• Segment distances: 39 km, 39 km, 39 km (equal).
• Speeds: 26, 39, and 52 km/h.

Concept / Approach:
Total distance = 117 km. Total time = 39/26 + 39/39 + 39/52 hours. Average speed = total distance / total time = 3 / (1/26 + 1/39 + 1/52) for equal d segments.

Step-by-Step Solution:

Verification / Alternative check:
Harmonic expression: V = 3 / (1/26 + 1/39 + 1/52) = 36 km/h.

Why Other Options Are Wrong:
33.33 and 35 are near-misses; 39 is the arithmetic mean, not applicable for equal-distance segments.

Common Pitfalls:
Averaging speeds directly; forgetting equal-distance condition.

Final Answer:
36 km/h