Question

A man walks at a speed of $6\text{km/h}$ for $1\text{km}$ and $8\text{km/h}$ for next $1\text{km}$. What is his average speed for the walk of $2\text{km}$?

• A. $5\text{km/h}$
• B. $6\text{km/h}$
• C. $7\text{km/h}$
• D. $8\text{km/h}$

Answer 1

The correct option is C $7\text{km/h}$

Distance travelled is $2\text{km}$
Time taken $=\frac{1\text{km}}{6\text{km/hr}}+\frac{1\text{km}}{8\text{km/hr}}$
Time taken $=\frac{1}{6}+\frac{1}{8}$ $=\frac{7}{24}\text{hr}$
Average speed $=\frac{2\text{km}\times 24}{7\text{hr}}$ $=\frac{48}{7}\text{km/hr}$
Average speed $\approx 7\text{km/hr}$