# Not sure what subject this comes under, and not HW, just a problem.

1. Jun 25, 2009

### bortonj88

1. The problem statement, all variables and given/known data
A plane travelling a distance of 660km, with unknown speed, has a tail wind of 60km/h, and due to this tail wind arrives at its destination 6 mins early.

What is the speed of the plane without the wind?

2. Relevant equations
I have so far used s=d/t,

3. The attempt at a solution
Using s=d/t, i have got expressions for both s and t.

s = (x + 16.7) m/s
t = (x' +360) s and i have converted 660 km into metres, 660000m to get

x + 16.7 = 660000/(x' + 360)

However i am not sure if this is the right way of looking at it, so any help will be greatly appriechiated.

Thanks
John

2. Jun 25, 2009

### HallsofIvy

Staff Emeritus
Where is the "16.7" from?

Why convert to meters?
Let v be the speed, in km/h, without the wind, t the time, in hours, to make the trip without the wind. Then 660/t= v or vt= 660. With the tail wind the speed is v+ 60 and the time for the trip is t- 1/10 (60 minutes is 1/10 hour). Then 660/(t- 1/10)= v+ 60 or 660= (t- 1/10)(v+ 60)= tv+ 60t+ v/10+ 6.

Solve the two equations vt= 660 and tv+ 60t+ v/10+ 6= 660.