Dev drives km at km/h and then km at km/h. What is his average speed for the whole journey?
Answer and explanation
Correct answer: B. 48 km/h
- Step 1: Time for the first part: h. Time for the second: h.
- Step 2: Total distance km, total time h.
- Step 3: Average speed km/h.
Answer
48 km/h.
Why not the others: 50 km/h: This takes the mean of and , ignoring that more time is spent at the slower speed. 24 km/h: This divides the product of the speeds by their sum, which is not an average speed. 100 km/h: This adds the two speeds together.
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