# Average speed

What is the average speed you have to move the way around the world in 80 days? (Path along the equator, round to km/h).

Result

v =  21 km/h

#### Solution:

$t = 80 \cdot \ 24 = 1920 \ \\ r = 6371 \ \\ s = 2 \pi \cdot \ r = 2 \cdot \ 3.1416 \cdot \ 6371 \doteq 40030.1736 \ \\ v = s/t = 40030.1736/1920 \doteq 20.849 = 21 \ \text { km/h }$

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#### Following knowledge from mathematics are needed to solve this word math problem:

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