Question

A car covers first $2km$ of the total distance of $4km$ with a speed of $30km/h$ and the remaining distance of $2km$ with a speed of $20km/h$. The average speed of the car is:

• A. $24km/h$
• B. $25km/h$
• C. $50km/h$
• D. $26km/h$

Answer 1

The correct option is A $24km/h$

First 2km distance :

Speed $v=30km/h$

Time taken $t_1=\frac{2}{30}=\frac{1}{15}h$

Next 2km distance :

Speed $v=20km/h$

Time taken $t_2=\frac{2}{20}=\frac{1}{10}h$

Total time $t=\frac{1}{15}+\frac{1}{10}=\frac{1}{6}$

Total distance $=4km$

Average speed $=\frac{4}{1/6}=24km/h$