The average speed for the journey from Llanfyllin to Bala is 14 km/h
Average speed is the ratio of total distance travelled to total time taken. Also, average speed can be given as the average of the different speeds.
Let d₁ represent the distance from Llanfyllin to Vyrnwy and t represent the time taken, since the speed is 12 km/h, hence:
12 = d₁/t
d₁ = 12t
Let d₂ represent the distance from Vyrnwy to bala and t represent the time taken. Since they spent the same time, since the speed is 16 km/h, hence:
16 = d₂/t
d₂ = 16t
Average speed = total distance/total time
Average speed = (d₁ + d₂) / (t + t)
Average speed = (12t + 16t) / 2t
Average speed = 28t / 2t
Average speed = 14 km/h
Hence their average speed for the journey from Llanfyllin to Bala is 14 km/h.
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