Question

a plane left 40 minutes late due to the bad weather and in order to reach the destination 1,600 km away in time it and increase the speed of 400 km hour from its actual speed find the speed of the plane​

Answer 1

Step-by-step explanation:

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Answer 2

Given Distance = 1600 km

Let the usual speed be x km/h

now, we know that 

speed = distance /time

time = distance / speed

Usual time = 1600/x

Now, due to bad weather the speed is increased b 400 km/ hr

new speed = 1600/x+400

Now it's given that the plane left 40 minutes late

new time = 1600/x+400 + 2/3 ( 40/60 = 2/3 hours)

1600/x = 1600/x+400 +2/3

1600/x-1600/x+400 = 2/3

1600(x+400)-1600x)/x(x+400) = 2/3

1600x + 640000-1600x/x²+400x = 2/3

640000 = 2/3(x²+400x)

640000 * 3/2 = x²+400x

960000 = x² +400x

0 = x²+400x-960000

0 = x² +1200x-800x-960000

0 = x( x+ 1200) - 800(x+1200)

0= (x+1200)(x-800)

x= -1200 or x= 800

Speed cannot be negative 

Hence, usual speed = 800 km/h