This is a very old joke, but still funny...
A Mathematician is on a boat and someone falls overboard.
"Help me, help me," cries a woman in the water.
The mathematician quickly grabs a life preserver and throws it to the woman. Once she grabs a hold of it, he pulls her in. Grateful at being rescued, she gives him a big hug.
The very next day the same woman falls overboard and begins to yell, "Help me, help me!"
The mathematician runs over, sees that it is the same woman and mumbles, "I've already solved this problem," as he walks away...
