Question

Hi friends solve this question

Answer 1

hlo mate hope it is helpfull to u if not then comment

Answer 2

Answer:

800 km/hr

Step-by-step explanation:

Let the speed of the plane be x km/hr.

Given, Distance = 1600 km.

∴ Time(t₁) = (1600/x) km/hr.

Given that it had to increase its speed by 400 km/hr.

So, New Speed = x + 400 km/hr.

∴ Time(t₂) = (1600/x + 400) km/hr.

Now,

Given that the plane left 40 mins late

⇒ (1600/x) - (1600/x + 400) = 40/60

⇒ (1600/x) - (1600/x + 400) = 2/3

⇒  1600[1/x - 1/x + 400] = 2/3

⇒ (320000)/x(x + 400) = 1/3

⇒ x² + 400x - 960000 = 0

⇒ x² + 1200x - 800x - 960000 = 0

⇒ x(x + 1200) - 800(x + 1200) = 0

⇒ (x + 1200)(x - 800) = 0

⇒ x = 800, -1200{Speed cannot be negative}

⇒ x = 800.

Therefore, usual speed of the plane is 800 km/hr.

Hope it helps!