Question

It takes Jack Frost 5 minutes to fly 35 minutes with the wind. It takes him 7 minutes to go 35 minutes against the wind. Determine his speed in still air (x) and the speed of the wind (y)

Answer 1

Answer:his speed in still air is 6 miles per minute.

the speed of the wind is 1 mile per minute.

Step-by-step explanation:

Let x represent his speed in still air.

Let y represent the speed of the wind.

It takes Jack Frost 5 minutes to fly 35 miles with the wind. This means that his total speed would be x + y

Distance = speed × time

It means that

35 = 5(x + y)

35 = 5x + 5y - - - - - - - - - - -1

It takes him 7 minutes to go 35 miles against the wind. This means that his total speed would be x - y

It means that

35 = 7(x - y)

35 = 7x - 7y - - - - - - - - - - -2

Multiplying equation 1 by 7 and equation 2 by 5, it becomes

245 = 35x + 35y

175 = 35x - 35y

Adding both equations, it becomes

420 = 70x

x = 420/70 = 6

Substituting x = 6 into equation 1, it becomes

35 = 5 × 6 + 5y

35 = 30 + 5y

5y = 35 - 30 = 5

y = 5/5 = 1