Question

Shakib, Ashraful and Mashrafee started a motorcycle race from Dhaka. Mashrafee
reached Khulna 10 minutes after Shakib and Shakib reached 20 minutes before
Ashraful. Speeds of Shakib and Ashraful were 60 km/hour and 20 km/hour
respectively. What was the speed of Mashrafee in unit of meter/hour?

Answer 1

Question #36781. Shakib, Ashraful and Mashrafee started a motorcycle race from Dhaka. Mashrafee reached Khulna 10 minutes after Shakib and Shakib reached 20 minutes before Ashraful. Speeds of Shakib and Ashraful were 60 km/hour and 20 km/hour respectively. What was the speed of Mashrafee in unit of meter/hour?

**Solution.**

x – the distance between Dhaka and Khulna.

Then time difference between the arrival of the Ashraful and Shakib:

$$\begin{array}{l} \frac{x}{20} - \frac{x}{60} = \frac{1}{3} \\ \frac{2x}{60} = \frac{1}{3} \\ 3x = 30, \quad x = 10. \end{array}$$

The distance between Dhaka and Khulna is 10 km. Shakib reached Khulna $\frac{10}{60} = \frac{1}{6}$ (hour) = 10 (minute).

Therefore, Mashrafee reached Khulna 20 minute. The speed of Mashrafee is $\frac{10}{20}$ (km/minute) = $\frac{10}{\frac{1}{3}} = 30$ (km/hour) = $30 * 10^3 = 30000$ (meter/hour).

**Answer:** 30000 (meter/hour).