A man was making a lot of noise in the kitchen! His wife came in and asked the reason. The man replied: "I am killing flies."

A little while later, his wife came back and saw that he was still making a lot of noise! She asked: "Well, how many flies have you killed so far?"

He said: "I have killed seven flies! 4 males and 3 females."

She said: "Ok, how can you tell the gender?"

He said: "Very easy: the 4 flies in my right hand are males. When I killed them, they were all on beer cans!" She asked: "If you are so smart, how can you tell the gender of the females?"

He said: "The three in my left hand were all on the phone!!!"