If a car travels first 30km at a uniform speed of 30km/hr and next 30km at a uniform speed of 60 km/hr . Calculate the average speed of car .
Answers
Answer:
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Explanation:
V1 = 60km/hr D1 = 30 km
T1 = ?
V2 = 40 km /hr D2 = 30 km
T2 = ?
Total Time = T1 + T2
We know that ,
velocity = Distance /Time
Therefore ,
V1 = D1/T1 or T1 = D1 / V1 => T1 = 30 km / 60 km /hr = 1/2 hr
V2 = D2/T2 or T2 = D2/ V2 => T2 = 30 km / 40 km /hr = 3/4 hr
Hence ,
Total Time = T1 + T2 = 1/2 + 3/4 = 5/4 hrs
we know that ,
Average Velocity = Total Distance / total time taken = 30 + 30 / 5/4
= 60/5/4 = 48 km /hr
Hence Average Velocity is 48km/hr and total time of journey = 5/4 hours.
My Short cut Method :-
When a body travels equal distance with different velocities V1 and V2 , then Average Velocity is Calculated as
Average Velocity = 2*V1*V2 / (V1 + V2 )
here , V1 = 60 km/hr and V2 = 40 km/hr
therefore ,
Average Velocity = 2*60*40 / (60+40 )= 4800/100 = 48km/hr
Also we know that ,
Average Velocity = Total Distance / Total Time Taken
48 = 60 / Total Time Taken
or Total Time Taken = 60/48 = 5/4 Hrs .
Answer:
The average speed of car is 40 kmph
Explanation:
Given:
Distance covered (Case I) = 30 km
Uniform speed (Case I) = 30 kmph
Distance covered (Case II) = 30 km
Uniform speed (Case II) = 60 kmph
Find :
The average speed of car
Solution :
First find the time
Time = distance / speed
★ Case I
Time = 30 / 30
1 hr.
★ Case II
Time = 30 / 60
0.5 (30 minutes)
Add Case (I) and (II)
1 hr. + 0.5
1hr 30 minutes
Total time = 1.5 hrs.
Total distance = Case (I) and (II)
30 km + 30 km
60 km
Now,
Find the average speed
Average speed = total distance / total time
60 km / 1.5 hrs.
40
The average speed of car is 40 kmph