An aeroplane flies along the four sides of a square field at the speeds of 150 km/h, 300 km/h, 450 km/h and 600 km/h. Find the average speed of the plane around the field.
Show answer & explanation
Correct answer: C
Explanation
The Correct answer is option 3 i.e. 288 km/h
As we know,
Average speed = Total distance/Total time
The square field's perimeter, four times the length of one of its sides, is the total distance the plane travels around the field.
Let's assume the length of one side of the square field is 's' kilometers.
So, the total distance covered is 4s kilometer
Time taken to cover each side:
1st side: s/150 hours
2nd side: s/300 hours
3rd side: s/450 hours
4th side: s/600 hours
Hence, Total time = s/150 + s/300 + s/450 + s/600 = (12s + 6s + 4s + 3s)/1800 = 25s/1800
Now, the average speed = 4s/(25s/1800) = 7200/25 = 288 km/h