The average speed of its entire journey is 81.8 KM/h

Step-by-step explanation:

GIVEN

A VEHICLE travels the first 40 km of its journey at an average speed of 60 km/h

The REMAINING 50km at an average speed of 100 km/h

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TO FIND

The average speed of its entire journey

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We know that,

Speed = Distance / Time

Distance = Speed × Time

Time = Distance / Speed

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We know that,

A vehicle travels the first 40 km of its journey at an average speed of 60 km/h

Distance = 40 km

Speed = 60 km/h

Time = ?

We know that,

Time = Distance / Speed

Time = 40 / 60

Time = 0.6

Time = 0.6 hours

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We know that,

The remaining 50km at an average speed of 100 km/h

Distance = 50 km

Speed = 100 km/h

Time = ?

We know that,

Time = Distance / Speed

Time = 50 / 100

Time = 0.5

Time = 0.5 hours

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Now

Let's find the average speed of entire journey

We know that,

Distance = 40 km + 50 km

Distance = 90 km

Time = 0.6 hours + 0.5 hours

Time = 1.1 hours

Speed = ?

We know that,

Speed = Distance / Time

Speed = 90 / 1.1

Speed = 81.8

Speed = 81.8 km/h

The average speed of its entire journey is 81.8 km/h