When Santa was a kid he wasn’t good with arithmetic, so his father sent him to a tutor.

Tutor: If I give you two pencils, and two pencils, and another two pencils, how many pencils do you have?

Santa: Seven!

Tutor: No, listen carefully again. If I give you two pencils, and two pencils, and another two pencils, how many pencils do you have?

Santa: Seven!

Tutor: Lets try this another way. If I give you two apples, and two apples, and another two apples, how many apples have you got?

Santa: Six!

Tutor: Good! Now, if I give you two pencils, and two pencils, and another two pencils, how many pencils have you got?

Santa: Seven!

Tutor: How on Earth do you work out that three lots of two pencils is seven?

Santa: I’ve already got one pencil at home!