An aeroplane flies along the four sides of a square at the speeds of 200, 400, 600 and 800km/hr. Find the average speed of the plane around the field? Choose the correct choice from the following options:
A) 384  B) 562  C) 458  D) 156  E) 452
Let the each side of the square is x km   average speed of plane is y km/hr   (x/200)+(x/400)+(x/600)+(x/800) = 4x/y   25x/2400 = 4x/y   y= 384 km/hr   384nswer is 384
<result>A</result>
An aeroplane flies along the four sides of a square at the speeds of 200, 400, 600 and 800km/hr. Find the average speed of the plane around the field?