A car runs in a triangular circuit with increasing speed in each of the three legs - first leg at 60km/hr , second leg at 120 km/hr and still faster in the final leg.
If the average speed over the entire circuit is 100km/hr, find the approximate speed in km/hr in
the final leg assuming that each leg is equal in length and comers are ignored.
Answers
Answer:
Step-by-step explanation:
Let the total distance travelled be x km Then total time taken =
10
x/3
+
20
x/3
+
60
x/3
=
30
x
+
60
x
+
180
x
=
180
6x+3x+x
=
180
10x
=
18
x
hrs Then average speed = =
Totaltimetaken
Totaldistancetravelled
=
x/18
x
km/hr = 18 km/hrTotal time for the journey, t=100/45=20/9 hrs
Time for first 50 km, t
1
=50/30=5/3 hr
So, time for remaining journey, t
2
=20/9−5/3=5/9 hrs
Speed for remaining journey v
2
=
5/9
50
=90 km/h
First -Third speed =10km/h
Second-Third speed =20km/h
So,Let Total distance =X
So,Total time = 30X + 60X + 180X
= 18X
So,Average Speed = Total distance is divided by the Total time =X× X18
=18km/h
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