Johny's mother ran into the bedroom when she heard him scream and found his two-year old sister pulling his hair.

She gently released the little girl's grip and said comfortingly to Johny,'There, there. She didn't mean it. She doesn't know that hurts.'

She was barely out of the room when the little girl screamed. Rushing back in,she asked, 'What happened?'  'She knows now,' Johny replied

Little Johnny returns from school and says he got an F in arithmetic. "Why?" asks the father. "The teacher asked 'How much is 2x3?' I said '6'"

"But that's right!"
"Then she asked me 'How much is 3x2?'" "What's the DAMN difference?" asks the father.
"That's what I said!