If a car went the first third of the distance at 10 kmh, the second third at 24 kmh, and the last ...

If a car went the first third of the distance at 10 kmh, the second third at 24 kmh, and the last third at 48 kmh, what was the average speed of the car for the entire trip?

Quiz

Answer/Solution

19 kmh

Steps/Work

Assume D/3 = 240 (this number is convenient because it is divisible by 10, 24 and 48)
So:
240 = 10*T1 = 24 hrs
240 = 24*T2 = 10 hrs
240 = 48*T3 = 5 hrs
T = T1 + T2 + T3 = 39 hrs
D = RT
(240*3) = R*39
R = 19
ANSWER: B

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If a car went the first third of the distance at kmh, the second third at kmh, and the last third at kmh, what was the average speed of the car for the entire trip?

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