Practice | Hashtable

Home > Practice > Arithmetic Aptitude > Average > Miscellaneous

1. A man travels equal distances of his journey at 40, 30 and 15 km/h. respectively. Find his average speed for whole journey.

A. 24

B. 25

C. 27

D. 28

Solution:

Required average speed,

= \frac{(3 \times 40 \times 30 \times 15)}{(40 \times 30) + (40 \times 15) + (30 \times 15)}

= 24 km/hr

Alternatively
Time taken to traveled

\frac{1}{3}

distance of journey with speed 40 kmph,

= \frac{\frac{1}{3}}{40} = \frac{1}{120}

Time taken to traveled

\frac{1}{3}

distance of journey with speed 30 kmph,

= \frac{\frac{1}{3}}{30} = \frac{1}{90}

Time taken to traveled

\frac{1}{3}

distance of journey with speed 15 kmph,

\begin{aligned} = \frac{\frac{1}{3}}{15} = \frac{1}{45} \\ Total time taken \\ = \frac{1}{120} + \frac{1}{90} + \frac{1}{45} \\ = \frac{45}{1080} \\ Average speed \\ = \frac{Total distance traveled}{Total time taken} \\ = \frac{1}{\frac{45}{1080}} \\ = 24 kmph \end{aligned}

You must login to add comments. Login now.