statistics

CPT 1344 views 2 replies

student

79 Points Joined April 2010

an aeroplane flies from A to B @ 500 km/hour and comes back from to B to A @ 700n km/hour. the average speed of the aeroplane is

i) 600 km./hour

ii) 583.33 km./hour

iii) 100 √35 km./hour

iv) 620 km./hour

Replies (2)

Chartered Accountant

14243 Points Joined February 2009

Let distance between A and B is 'X' kms

so, time taken to travel from A to B = 'x' / 500 ( Time = distance / speed)

similarly, time taken to travel from B to A = 'x' / 700 ( Time = distance / speed)

so total distance traveled= x + x = 2x

therefore, speed = distance / time = 2x / [ x /500 + x /700] = 2 / [1/500+ 1/700] = 583.33 kms

60 Points Joined August 2008

Let us assume the distance from A to B to be 3500 Kms. (L.C.M. of 500 & 700)

SPEED DISTANCE TIME

500 Km / Hr. 3500 Kms. 7 Hrs.

700 Km/Hr. 3500 Kms. 5 Hrs.

Total 7000 Kms. 12 Hrs.

Average Speed = Total Distance / Total Time = 7000 Kms / 12 Hrs. = 583.33 Kms. / Hr.

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