Question

A car traveled the first third of distance S at speed of 10 ms', the second third at a speed
of 20 m s'and last third at a speed of 60 m s. Determine average speed of car.
S 3
S 3
S/3
+
10
20
A
B
D
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Answer 1

Answer:

18 m/s

Explanation:

For 1st 3rd:

→ speed = distance/time

→ 10 = (S/3)/time

→ time = (S/3)/10 = S/30

For 2nd 3rd:

→ 20 = (S/3)/time

→ time = (S/3)/20 = S/60

For last 3rd:

→ 60 = (S/3)/time

→ time = (S/3)/60 = S/180

Total distance = S

Time = (S/30) + (S/60) + (S/180) = (S/18)

Hence,

→ speed = S/(S/18) = 18 m/s