Interesting and learned little joke.

1. One day, the teacher asked Xiao Ming 1+ 1=? Xiao Ming said he didn't know. The teacher asked Xiaoming to go home and ask his parents. He came home and his father was watching a football match. Xiao Ming asked his father 1+ 1=? Who did dad say that foreigner was? Mom is cooking, and Xiaoming asks 1+ 1=? Mom said, alas! The food is burnt. The next day, the teacher asked Xiao Ming 1+ 1=? Xiao Ming answers who is that foreigner? The teacher asked again 1+ 1=? Xiao Ming said, alas! The food is burnt.