Question

$A$ car travels a distance of $45$ km at a speed of $15$ km/hr. It covers the next $50$ km of its journey at the speed of $25$ km/hr and the last $25$ km of its journey at the speed of $15$ km/hr. What is the average speed of the car?

• A. $40$ km/hr
• B. $24$ km/hr
• C. $15$ km/hr
• D. $18$ km/hr

Answer 1

The correct option is D $18$ km/hr

Total time taken $=\frac{45}{15}hrs+\frac{50}{25}hrs+\frac{25}{15}hrs=3hrs+2hrs+\frac{5}{3}hrs=\frac{20}{3}hrs$

$\therefore$ Average speed of the car $=30\times \frac{45+50+25}{20}$

$=\frac{120\times 3}{20}km/hr=18km/hr$.