Solution
Given:• An aircraft makes a to-and-fro journey every day between the capital cities of two countries M and N, at an average speed of 500 mph
• Distance between M and N is 2200 miles
• On a certain day, while returning from N to M, the aircraft faced bad weather and made an emergency landing in P
• City P is 2000 miles away from city N and 600 miles away from city M
• Because of bad weather, the speed of the aircraft becomes 400 mph from N to P
To find:• The average speed of the aircraft in the whole journey
Approach and Working: • The whole journey is divided into three separate parts:
o From M to N – onward journey at normal speed of 500 mph
o From N to P – 1st part of return journey at a speed of 400 mph
o From P to M – 2nd part of the return journey at a speed of 500 mph
This can be demonstrated as follows:

• Therefore, the total journey distance of the aircraft = (2200 + 2000 + 600) miles = 4800 miles
• As we already know the distances and individual speed for every part of the journey, let’s calculate the time taken for the journey
• For the onward journey M to N, the aircraft covered 2200 miles distance at 500 mph
o Therefore, the time taken in the onward journey = \(\frac{2200}{500}\) hrs = 4.4 hrs
• For the 1st part of the return journey N to P, the aircraft covered 2000 miles distance at 400 mph
o Therefore, the time taken in the 1st part of the return journey = \(\frac{2000}{400}\) hrs = 5 hrs
• For the 2nd part of the return journey P to M, the aircraft covered 600 miles distance at 500 mph
o Therefore, the time taken in the 2nd part of the return journey = \(\frac{600}{500}\) hrs = 1.2 hrs
• Hence, the total journey time = (4.4 + 5 + 1.2) hrs = 10.6 hrs
• Therefore, the average speed of the whole journey = total distance travelled/total time taken = \(\frac{4800}{10.6}\) mph = 452.8 mph
Hence, the correct answer is option B.
Answer: B