A train runs for 3 hours at a speed of 60 km per hour and for the next 2 hours at a speed of 80 km per hour. Find the average speed of the train for the 5-hour journey.
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Answers
Answer:
your answer
Step-by-step explanation:
train has a speed of 60km/h for the first one hour,
t
1
=1hr, v
1
=60km/hr
Distance covered by the train, d
1
=v
1
t
1
d
1
=60×1=60km
For the next half hour, train has speed 40km/hr
v
2
=40km/hr, t
2
=0.5hr
d
2
=v
2
t
2
d
2
=40×0.5=20km
Total distance, d=d
1
+d
2
d=60+20=80km
Total time, t=t
1
+t
2
t=1hr+0.5hr=1.5hr
Average speed, v
avg
=
t
d
v
avg
=
1.5hr
80km
=53.33km/hr
The correct option is B
Step-by-step explanation:
distance for first part of journey = 60 x 3 = 180 km
distance for second part of journey = 80 x 2 = 160 km
total distance = 180 + 160 = 340 km
total time = 3 + 2 = 5 hours
average speed = total distance traveled ÷ total time taken
average speed = 340 ÷ 5 = 68 km per hour