Question

a train travels 20 km at a uniform speed of 60 km h-1 and the next 20 km at a uniform speed of 80 km h-1. calculate its average speed.

Answer 1

Here is your answer mate:

Time taken to travel 20 km at 60km/hr=20/60=0.33hr
time taken to travel nxt 20 km at 80km/hr=20/80=0.25hr
avg speed=total distance travelled / total time taken=40/0.58=68.96km/hr
                                                                                           ≈69km/hr

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Niki...... :-)

Answer 2

average speed =total distance / total time

time t1 for first interval = 20÷60
time t2 for 2nd interval = 20÷80
t1=1/3
t2=1÷4
avg speed = (20+20)/(1/3+1/4)

(40×12)/7
480÷7
=68.57


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