6. A car travels first 30 km with a uniform speed of 60 km h-1 and then next 30 km with a uniform speed of 40 km h-1. Calculate : (i) the total time of journey, (ii) the average speed of the car. Ans. (i) 75 min, (ii) 48 km h-1.
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Complete step by step answer:
Find the total time taken:
S=DT .
Here:
S = Speed.
D = Distance.
T = Time Taken.
For the first 30km.
T1=D1S1.
⇒T1=3060.
Time required to cover first 30 km is:
⇒T1=12hr=30min.
Similarly, Time required to complete the next 30km.
T2=D2S2.
Put in the given value in the above equation and solve,
⇒T2=3040.
Time required to cover the next 30 km is:
⇒T2=34hr=45min.
Total time taken to cover 60km is:
T=T1+T2.
Add the two times that we have found out:
⇒T=45+30.
The time taken is:
⇒T=75min.
Option B is correct. A car travels first 30 km with a uniform speed of 60kmh−1and then next 30 km with a uniform speed of 40kmh−1. The total time journey it takes is 75 min.
Hope it helps you thanks
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