Question

A bus travels 30 km at a uniform speed of 40 km/h and the next 30 km at a uniform speed of 20 km/h.The average speed of the bus is

• A. 26.6 km/h
• B. 36.8 km/h
• C. 25 km/h
• D. 28.9 km/h

Answer 1

The correct option is A 26.6 km/h

average velocity=$\frac{totaldisplacement}{totaltimetaken}$

for first 30 km time elapsed is= displacement/ velocity =30/40 = 3/4h

for next 30 km time elapsed is =displacement/velocity= 30/20 = 3/2h

thus average velocity

av= $\frac{30+30}{\frac{3}{4}+\frac{3}{2}}=\frac{60}{\frac{9}{4}}=\frac{80}{3}=26.66km/h$

Option A is correct