If a person has to drive 210 km, how long will the journey take if he drives at an average speed of 20 km/hr for 120 km and at an average speed of 30 km/hr for 90 km, and have a 60 minutes stop for refreshments midway through the journey?

Correct Answer: (D) 10 hours

The driving time for the first segment is $\frac{120\text{ km}}{20\text{ km/hr}}=6\text{ hours}$$\frac{120 \text{ km}}{20 \text{ km/hr}}$ = 6 $\text{ hours}$. The driving time for the second segment is $\frac{90\text{ km}}{30\text{ km/hr}}=3\text{ hours}$$\frac{90 \text{ km}}{30 \text{ km/hr}}$ = 3 $\text{ hours}$. Adding the 60-minute (1 hour) refreshment stop midway, the total journey time is $6 + 3 + 1 = 10$$\text{ hours}$.