Question

You drive 6.0 km at 50 km/h and then another 6.0 km at 90 km/h. Your average speed over the 12 km drive will be ____

Answer 1

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

$t = \dfrac{d}{v}$

Put the value in to the formula

$t=\dfrac{6.0}{50}$

$t=0.12\ hr$

We need to calculate the time in another distance

Using formula of time

$t = \dfrac{d}{v}$

Put the value in to the formula

$t=\dfrac{6.0}{90}$

$t=0.067\ hr$

We need to calculate the average speed

Using formula of average speed

$v=\dfrac{D}{T}$

Where, D = total distance

T = total time

Put the value into the formula

$v=\dfrac{12}{0.12+0.067}$

$v=64.17\ km/hr$

Hence, The average speed is less than 70 km/h.