Question

From 10:00 PM to 11:00 PM, a person drove at $40km/h$ and from 11:00 PM to 12 midnight at $50km/h$. What is his average speed in the time interval 10 PM to 12 AM?

• A. 50 km/h
• B. 45 km/h
• C. 40 km/h
• D. 90 km/h

Answer 1

The correct option is B

45 km/h

Given:
Speed in the time interval 10 PM to 11 PM = $40km/h$
Speed in the time interval 11 PM to 12 AM = $50km/h$

Distance is given as the product of speed and time.
The time intervals are equal to 1 hour.
Distance covered in the time interval 10 PM to 11 PM = $40km$
Distance covered in the time interval 11 PM to 12 AM = $50km$

Total distance $=40+50=90km$

Total time taken = $2hours$

Average speed is the ratio of total distance to the total time.
$v=\frac{90}{2}=45km/h$