A car travels 40 km at a uniform speed of 40km/h . What should be it's speed for the next 80 km if the average speed for entire journey is 60 km/h . Pls tell
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جانگس جاگوچا ناجائز کاجگاطس نسجسگ
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40 km at= 40km/h
time taken = distance÷time
=40÷40
=1 hour
time taken to cover 40km at 40km/h=1 hour
Now let car speed was "X" km/h for next 80 km
speed = X km/h
distance =80km
time =80÷x
time = 80/x hour
total distance =40+80=120
total time = 1+80/x hour
average speed given :: 60km/h
average speed=total distance÷total time
60=120÷[x+80/x]
60=120×x/x+80
60(x+80)=120x
60x+4800=120x
4800=120x-60
4800=60x
X=4800/60
X=80
speed for next 80kmshould be =80km/h
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