Question

a car travel first 30 km with a uniform speed of 60 km h and then next 30 km with a uniform speed of 40 km h. calculate i. the total time of journey. ii. the average speed of the car

Answer 1

Answer :
         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 .


This was my Previous Solution !!
@Moderators Kindly Check before Deleting !! There are many ways to solve a given problem !!!

Cheers !!!
Ime !!!! :)
    

Answer 2

Explanation:

this is the answer , please mark it as brainlist