A sales agent travels a distance of 50 km in 2 hours and 30 minutes. How much faster, in kilometers per hour, on average, must he travel to make such a trip in 5/6 hours less time?

10

The correct answer is Option (4) → 10

Given:

• Distance = 50 km
• Original time = 2 hours 30 minutes = 2.5 hours

Original average speed

$\text{Speed}_1 = \frac{50}{2.5} = 20 \text{ km/h}$

The trip is to be completed in $\frac{5}{6}$​ hour less time:

$\text{New time} = 2.5 - \frac{5}{6} = \frac{15 - 5}{6} = \frac{10}{6} = \frac{5}{3} \text{ hours}$

New average speed

$\text{Speed}_2 = \frac{50}{5/3} = 50 \times \frac{3}{5} = 30 \text{ km/h}$

Increase in speed

$30 - 20 = 10 \text{ km/h}$