You will probably get the right answer with the formula for PSR
(point of safe return):
time to PSR= (HE)/(O+H)
where
H= groundspeed home
O= groundspeed outbound
E= endurance without reserves
You do need a wheel because the answers are close together.
If you don't have one with you use 7 knots wind component for the first question, but this doesn't give an accurate answer.
Last edited by Da-20 monkey; 3rd Jan 2012 at 06:21.