Question

carr Travels first 30 kilometre with a uniform speed of 40 km per Hour and next 30 km at a uniform speed of 20 km per hour find the average speed and total time of the
journey
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Answer 1

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Answer 2

Average speed is 26.67 km/h and total time of journey is 2.25 hours.

Explanation :

At first let's find time taken in first part :-

● Distance = 30 km.

● Speed = 40 km/h

● Time = ?

We know,

● Speed = Distance/Time

⇒ 40 = 30/Time

⇒ 40 × Time = 30

⇒ Time = 30/40

⇒ Time = 3/4 hours.

Now let's find time taken in the second part :-

● Distance = 30 km

● Speed = 20 km/h

● Time = ?

Now,

⇒ 20 = 30/Time

⇒ 20 × Time = 30

⇒ Time = 30/20

⇒ Time = 3/2 hours.

Now we know that,

Av. speed = Total distance/Total time

⇒ Av. speed = (30 + 30)/(3/4 + 3/2)

⇒ Av. speed = 60/{(3 + 6)/4}

⇒ Av. speed = 60/(9/4)

⇒ Av. speed = 60 × (4/9)

⇒ Av. speed = 240/9

⇒ Av. speed = 26.67 km/h

∴ Average speed of car = 26.67 km/h

Now let's find total time of journey :-

⇒ Total time = 3/4 + 3/2

⇒ Total time = (3 + 6)/4

⇒ Total time = 9/4

⇒ Total time = 2.25 hours

∴ Total time of journey = 2.25 hours.