math
posted by Lindsay on .
a cyclist travels the 30 km from Town A to Town B at an average speed of 25 km/h and immediately continues the journey to town C, which is a further 60 km away at an average speed of 20 km/h.
What is the average speed for the whole journey?

total distance = 30+60 km
total time = 30/25 + 60/20 = 21/5 hr
avg speed = 90km รท 21/5 hr = 150/7 km/hr 
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