a train travels 20 km ata a uniform speed of 60 km/hr and next 20 km ata a ubiform speed of 80 km/hr calculate its average speed
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distance covered by the train at first (d1)=20km
speed of train then(s1)=60km/hr
time required to cover 20km (t1)=d1/s1= 20/60=1/3hrs
next distance covered by the train (d2)=20km
speed of the train then(s2)= 80km/hr
time required to cover next 20km (t2)=d2/s2= 20/80=1/4 hrs
therefore,
average speed = d1+d2 / t1+t2= 40/(7/12)=40×12/7= 480/7km/hr
speed of train then(s1)=60km/hr
time required to cover 20km (t1)=d1/s1= 20/60=1/3hrs
next distance covered by the train (d2)=20km
speed of the train then(s2)= 80km/hr
time required to cover next 20km (t2)=d2/s2= 20/80=1/4 hrs
therefore,
average speed = d1+d2 / t1+t2= 40/(7/12)=40×12/7= 480/7km/hr
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