A motorist travelled 2/5 of his journey in 4/5 hr. He travelled the remaining 84 km in 1 1/5 hr.
Find the avergage speed for his whole journey.
To find average speed, we need 2 things, “ total distance” and “total time”.
1 – 2/5 = 3/5 -> remaining journey
3/5 of his journey = 84 km
1/5 of his journey = 84 / 3 = 28 km
5/5 of his journey = 28 * 5 = 140 km ( total distance )
Total time taken = 4/5 + 1 1/5 = 2 hrs
Hence
Average speed = Total distance / total time
= 140 / 2
= 70 km / h.
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