Post #1663514
2026-04-23 21:27 UTC
A car travels from point A to point B with a speed of 50km/h and then travels back to A with a speed of 100km/h. What's the average speed of the car for the whole distance?
#math
Replies (2)
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@geoffl@mastodon.me.uk 2026-04-23 21:42
@rtn 66⅔mph
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@tty@sunbeam.city 2026-04-23 22:56
@rtn Hehe. It's one of those problems that tempts you to use System 1 (quick) brain, but requires System 2 (slow) brain. Speed = Distance / Time = D / T Given D / T = 50 km/hr Given D / (T/2) = 100 km/hr AvgSpeed = 2D / (T+T/2) Let D = 50 km So, T = 1 hr AvgSpeed = 2(50) / (1 + 1/2) AvgSpeed = 100 / 1.5 AvgSpeed = 66.6̅ km/hr