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Question

Hi would appreciate if i could get help with this question:

A man jogs 3.75 km at an average speed of 9 kilometres per hour for the first part of the journey and then walks 70 metres in 50 seconds for the second part of the journey.

Find the average speed for the whole journey.

Thank you!

Answer

3.75/9 = 5/12 h
70 m = 0.07 km
50 s = (1/72) h
3.75 + 0.07 = 3.82 km
(5/12) + (1/72) = 31/72 h
3.82/(31/72) = 27504/3100 = 8.87 (2 dp)

Ans : 8.87 km/h (2dp).

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Average Speed = Total Distance / Total Time

Total Distance

70m = 0.07km
3.75km + 0.07km = 3.82km

Total Time

50s = 0.8min

1/9 x 3.75 + (0.8/60) = 0.43 hour

Average Speed

3.82/0.43 = 8.88372 km/hr (5 d.p.)
= 8.88km /hr (2 d.p.)

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