Question

A car moving on a straight road covers one third of the distance with 20 km/hr and the rest with 60 km/hr. The average speed is

• A. 40 km/hr
• B. 80 km/hr
• C. $46\frac{2}{3}$ km/hr
• D. 36 km/hr

Answer 1

The correct option is D

36 km/hr

Average speed = $\frac{Totaldistance}{Totaltime}$

$=\frac{x}{t_1+t_2}$

= $\frac{x}{\frac{\frac{x}{3}}{v_1}+\frac{\frac{2x}{3}}{v_2}}$

$=\frac{1}{\frac{1}{3\times 20}+\frac{2}{3\times 60}}$

$=36$ km/hr