1. Who is it?
A man on a park bench is looking at a small portrait. You ask him, "Who is that in the picture?"
The man says, "Brothers and sisters I have none, but that man's father is my father's son."
Can you tell what person is in the picture?
From Mathsisfun.com
Answer: His son

2. Coloured shirts
At a restaurant downtown, Mr. Red, Mr. Blue, and Mr. White meet for lunch. Under their coats they are wearing either a red, blue, or white shirt.
Mr. Blue says, "Hey, did you notice we are all wearing different coloured shirts from our names?"
The man wearing the white shirt says, "Wow, Mr. Blue, that's right!"
Can you tell who is wearing what color shirt?
From Mathsisfun.com
Answer:
The person in the white shirt can only be Mr. Red or Mr. Blue. Since the person wearing the white shirt is talking to Mr. Blue, he cannot be Mr. Blue, so he is Mr. Red. Similarly, Mr. Blue cannot be wearing a blue shirt, so he is wearing either red or white. Since Mr. Red is wearing the white shirt, Mr. Blue is wearing the red shirt. So the last person (who did not need to speak or be seen!) is Mr. White and he is wearing a blue shirt.

3. Coloured marbles (there are two pictures, one for puzzle and one for solution)
Arrange these six marbles so that each one touches all four marbles of a different colour.
From Mathsisfun.com
Answer: The six marbles have to be arranged as vertices of an octahedron.

4. Coin-cidence (has three pics, two for puzzle and one for solution)
Look at the triangle of six coins in the picture.
I want to turn this triangle upside-down, as shown.
What is the smallest number of coins I must move?
From Mathsisfun.com
Answer: Just two. See picture.