Question

A bus travels the first one-fourth of a certain distance with a speed of 20 km/hr, the next one-fourth distance with a speed of 40 km/hr, and the last one-half distance with a speed of 120 km/hr. What is the average speed of the bus for the whole journey?

• A. 43 (7/11)kmph
• B. 45 (5/11) kmph
• C. 40 (10/11) kmph
• D. 36 (4/11) kmph
• E. None of these

Answer 1

The correct option is A

43 (7/11)kmph

Let distance be 'd'.

Average Speed = Total distance/Total time

$\Rightarrow$ Average Speed = $\frac{d}{\frac{d}{4\times 20}+\frac{d}{4\times 40}+\frac{d}{2\times 120}}$

$\Rightarrow$ Average Speed = $\frac{d}{\frac{11d}{480}}$

$\Rightarrow$ Average Speed = 43$\frac{7}{11}$ kmph