Answer: 333.33km
Explanation:
Average speed is calculated as:
= Distance / Time
Since Alex takes 30 minutes to travel 50 km in her car, Alex average speed will be:
= 50km / 30minutes
= 50km / 0.5hour
= 100km/hour
Since Alex drives at an average speed that is 2/5 of the average speed that Roy's train travels. Roy's average speed will be:
= 100 ÷ 2/5
= 100 × 5/2
= 250km/hour
Since Roy travels for 1 hour and 20 minutes on his train, his distance travelled will be:
= Speed × Time
= 250 × 1 hour 20 minutes
= 250 × 1 20/60
= 250 × 1 1/3
= 250 × 4/3
= 1000/3
= 333.33km
Roy travels 333.33km