Respuesta :
Option B
The rate of the plane in still air and the rate of the wind is 180 miles per hour and 20 miles per hour respectively
Solution:
Given that, A plane flew 800 miles in 4 hours with the wind.
It took 5 hours to travel the same distance against the wind.
We have to find what is the rate of the plane in still air and the rate of the wind?
Let the speed of plane in still air be m and speed of wind be n.
Now, we know that, distance = speed x time.
Then, while travelling with wind ⇒ 800 = ( m + n ) x 4 ⇒ m + n = 200 ⇒ (1)
And, while travelling against wind ⇒ 800 = ( m – n ) x 5 ⇒ m – n = 160 ⇒ (2)
Now, solve the equations (1) and (2)
(1) ⇒ m + n = 200
(2) ⇒m – n = 160
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(+) 2m + 0 = 360
2m = 360
m = 180
Now, substitute the m value in (1)
180 + n = 200 ⇒ n = 200 – 180 ⇒ n = 20
Hence, the speed of plane in still air is 180 miles per hour and speed of wind is 20 miles per hour. Thus option B is correct
