1. The problem statement, all variables and given/known data A parachutist leaps from a hovering helicopter, after 4.0s of freefall shouts back at 425Hz. What frequeny is heard at the helicopter? 2. Relevant equations f'=f/(1+Vs/V) Vsource=? f'=? f=425Hz V=343m/s 3. The attempt at a solution I'm stuck on finding the speed for the jumper. I'm sure it's simple but i just can't think of it for somereason.