Conservation of Momentum of a boat and women

[negatifzeo]

Homework Statement

I'm getting fairly frustrated seeing as I've been working on this 'easy' problem for several hours yet still can't get the correct solution. The problem is as follows:
A 180 lb- man and a 120-lb woman stand side by side at the same end of a 300-lb boat, ready to dive, each with a 16 ft/s velocity relative to the boat. Determine the velocity of the boat after they have both dived if the woman dives first.

Homework Equations

Total initial momenta=total final momenta

The Attempt at a Solution

First, the woman dives.
0=480(v) +120(16) b=-4 ft/s

Second, the man dives:
(300+180)(-4)=(180)(16)+300(Vf) I keep getting Vf=-16, the book says it is supposed to be -9.2. Can anyone tell me what I am doing wrong?

 

[aim1732]

You have used velocity of man relative to boat in an eqn. along with velocities w.r.t ground?