Question

An aeroplane flying with a speed with a wind of 30 km / hr takes 40 mins less to fly 3600 km , than what it would have taken to fly against the same wind . Find the Planes speed of flying in still air .


Hint = { 3600 / ( x - 30 ) } - { 3600 / ( x + 30 ) } = 2/3 .


Chap --> Quadratic Equation class 10 .

Plz help !!!

Answer 1

according to the que,
3600/x-30 -3600/x+30=40/60
3600*(x+30-x+30)/x^2-900=2/3
60*5400=x^2-900
therefore x^2=324900
x=570km/hr

Answer 2

Answer:

Speed of plane in still air is 570 km/hr.

Step-by-step explanation:

Given:

Speed of wind = 30 km/hr

Time taken by plane when flying in direct of wind = 40 minutes less than time taken by plane when flying against the wind.

Distance covered by plane = 3600 km

To find: Speed of the plane in still air.

Let x be the speed of plane in still air.

40 min = 2/3 hr

According to the Question,

$\frac{3600}{x-30}-\frac{3600}{x+30}=\frac{2}{3}$

$\frac{3600(x+30)-3600(x-30)}{(x-30)(x+30)}=\frac{2}{3}$

$\frac{3600x+108000-3600x+108000}{x^2-900}=\frac{2}{3}$

$\frac{216000}{x^2-900}=\frac{2}{3}$

$3\times216000=2(x^2-900)$

$2x^2-1800=648000$

$2x^2=648000+1800$

$x^2=\frac{649800}{2}$

$x^2=324900$

x = 570

Therefore, Speed of plane in still air is 570 km/hr.