An aeroplane flying 1000 km covers the first 200 km at the rate of 200 km/hr,…
2023
An aeroplane flying 1000 km covers the first 200 km at the rate of 200 km/hr, the second 200 km at 400 km/hr, the third 200 km at 600 km / hr & last 200 km at the rate of 800 km/hr. Determine the average speed of the aeroplane.
- A.
250 km/hr
- B.
300 km/hr
- C.
480 km/hr
- D.
384 km/h
Attempted by 11 students.
Show answer & explanation
Correct answer: D
Average speed is calculated as:
Average Speed = Total Distance ÷ Total Time
Step 1: Calculate the time taken for each segment.
Time for first 200 km = 200 ÷ 200 = 1 hour
Time for second 200 km = 200 ÷ 400 = 0.5 hour
Time for third 200 km = 200 ÷ 600 = 1/3 hour
Time for last 200 km = 200 ÷ 800 = 0.25 hour
Step 2: Calculate the total time.
Total time = 1 + 0.5 + 1/3 + 0.25
Taking LCM = 12,
Total time = (12 + 6 + 4 + 3)/12
= 25/12 hours
Step 3: Calculate the average speed.
Average Speed = 800 ÷ (25/12)
= 800 × 12/25
= 384 km/h
Therefore, the average speed of the aeroplane is 384 km/h.
None of the given options is correct.