Question

An airplane took 2 hours to fly 600 km against a head wind. The retrun trip with the wind took 1 and two thirds hours. Find the speed of the plane in stll air.

Answer 1

The speed of plane in still air is 330 kmph

Explanation:

Given as :

The distance cover against the wind = 600 km

The time taken against the wind = 2 hours

The distance cover with the wind = 600 km

The time taken with the wind = ( 1 +
`(2)/(3)` ) hours

=
`(5)/(3)` hours

Let The speed against the wind = x - y kmph

The speed with the wind = x + y kmph

where x is the speed of plane in still air

And y is the speed of wind

So , Speed =
`(\texrm Distance)/(\texrm Time)`

Or, x - y =
`(600)/(2)` = 300 ......A

And x + y =
`(600)/((5)/(3) )`

Or , x + y = 360 .......B

From eq A and B

( x + y ) - ( x - y ) = 360 - 300

Or, 2 y = 60

∴ y =
`(60)/(2)` = 30 kmph

And x = 360 - 30 = 330 kmph

Hence The speed of plane in still air is 330 kmph Answer