You drive 6.0 km at 50 km/h and then another 6.0 km at 90 km/h. your average speed over the 12 km drive will be

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23-08-2017
Mathematics

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You drive 6.0 km at 50 km/h and then another 6.0 km at 90 km/h. your average speed over the 12 km drive will be

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0100010 0100010 · Answer 1 · 2017-08-23T08:25:42+02:00

0100010 0100010

23-08-2017

v1=50km/h
v2=90km/h
s1=s2=6km
s=12km

The average speed over the 12 km drive:
v=s/t

The time needed to drive 12km will be:
t = t1+t2

t1=s1/v1, t2=s2/v2

t=s1/v1+s2/v2=(s1v2+s2v1)/(v1v2)

v=sv1v2/(s1v2+s2v1)=12*50*90/(6*50+6*90)=64,28 km/h

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