A car travels the first 50km of its journey at an average speed of 25m/s snd the next 120km at an average speed of 80km/h. The car completes the lat part of its journey at an average speed of 90km/h in 35 minutes. Find the average speed for its entire journey ,giving your answer in km/h.

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debrubs97 debrubs97 · Answer 1 · 2019-10-24T22:30:14+02:00

Answer:

84,6km/h

Step-by-step explanation:

the whole journey was

in the first part the car travels 50km, in the second part 120km and in the third part we can find it with a simple rule of three

90km--->60 min

X<--------35min= 52.5 km the car made in the last part

50km+120km+52,5km=222.5km was all the journey

and he made it in:

the last part in 35min,
in the second part we know that the car was going at 80km/h and that he made 120km so:

80km--->60 min

120km--->90 min

in the first part we know that the car was going at 25m/s and he made 50km. 25m/s*1km/1000m*3600s/1h= we obtain the speed in km/h=90km/h

90km---->60min

50km---->x=33,333 min

The whole journey last 33,333min+90min+35min=158.333min

if we express that in hour = 158.333min*1hr/60min=2.63

the car made 222.5km in 2.63 hour

so the average speed was

222.5---->2.63hr

X--------1hr=84,6

the average speed was 84,6km/h