Question

A person travels a total distance in three parts in the ratio 4:3:1 with a constant speed of 90km/h,20m/s and 10m/s respectively. What will be the average speed of the journey?

Answer 1

Answer :

Given -

• The Distance travelled is in the ratio of 4:3:1
• First part is travelled at the speed of 90 km/hr
• Second part is travelled at the speed of 20 m/s
• Third party is travelled at the speed of 10 m/s

To Find -

• Average Speed ?

Solution -

Let the distances travelled be 4x, 3x and x.

So, First part of distance 4x is travelled with speed of 90 km/hr (90*5/18 = 25 m/s).

The second part of distance 3x is travelled with speed of 30 m/s.

The third part of distance x is travelled with speed of 10 m/s.

Now, Finding the time in each case.

Case 1 :

Time = 4x/25 s

Case 2 :

Time = 3x/30 s

Case 3 :

Time = x/10 s

Average Speed = Total Distance/Total Time

⇒ Avg. Speed = (4x + 3x + x)/(4x/25 + 3x/30 + x/10)

⇒ Avg. Speed = 8x/(24x + 15x + 15x)/150

⇒ Avg. Speed = 8x/(54x/150)

⇒ Avg. Speed = 8x*150/54x

⇒ Avg. Speed = 150/6.75

⇒ Avg. Speed = 22.22 m/s

Average Speed of the journey is 22.22 m/s.

Answer 2

Answer: Average speed = 800/41 = 19.512m/s

Explanation: