Answer:
The average speed is less than 70 km/h.
(B) is correct option.
Explanation:
Given that,
distance = 6.0 km
Speed = 50 km/h
Speed = 90 km/h
We need to calculate the time in 6.0 km distance
Using formula of time
[tex]t = \dfrac{d}{v}[/tex]
Put the value in to the formula
[tex]t=\dfrac{6.0}{50}[/tex]
[tex]t=0.12\ hr[/tex]
We need to calculate the time in another distance
Using formula of time
[tex]t = \dfrac{d}{v}[/tex]
Put the value in to the formula
[tex]t=\dfrac{6.0}{90}[/tex]
[tex]t=0.067\ hr[/tex]
We need to calculate the average speed
Using formula of average speed
[tex]v=\dfrac{D}{T}[/tex]
Where, D = total distance
T = total time
Put the value into the formula
[tex]v=\dfrac{12}{0.12+0.067}[/tex]
[tex]v=64.17\ km/hr[/tex]
Hence, The average speed is less than 70 km/h.
