# 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

1
by sreya394 04.06.2015

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the average speed of the car

1
by sreya394 04.06.2015

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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 !!!! :)

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 ,

we know that ,

= 60/5/4 =

Hence Average Velocity is 48km/hr and total time of journey = 5/4 hours.

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 ,

Also we know that ,

Average Velocity = Total Distance / Total Time Taken

48 = 60 / Total Time Taken

or

This was my Previous Solution !!

@Moderators Kindly Check before Deleting !! There are many ways to solve a given problem !!!

Cheers !!!

Ime !!!! :)