Joe flew 300 miles with the wind in two hours. After flying against the wind for 2 hours, he had made 270 miles of the return trip. Find the wind speed and the speed of the plane in still air.

with - r * t = d

against-

This is a motion problem but I don't know how to do it.

SmartMathMan May 7, 2019

#1**+2 **

When flying WITH the wind his rate is s +w where s = plane speed w = wind speed

so d = r * t

300 = (s+w) * 2

AGAINST the wind, his rate is s - w

so 270 = (s-w)*2 Now you have two equations and two unknowns....solve the system of equations to find ' s '

ElectricPavlov May 7, 2019

#4**+2 **

it is supposed to be the box way of solving it, nevermind. But I can't solve a problem with two variables.

SmartMathMan
May 7, 2019

#6**+1 **

It is WAY easier to solve this NOT using the clumsy box method:

You have two equations:

300 = 2(s+w) or 150 = s+w (by dividing both sides of the equation by 2)

270 = 2 (s-w) or 135 = s-w <------ Now ADD the two equations together

285 + 2s thus s = 142.5 = plane speed in still air

I havn't any idea how to make this into a quadratic to solve by the Box method

(this ' box method', I think is crazy....sorry you are being taught this method)...

ElectricPavlov May 7, 2019