Which number should replace the question mark?

Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?"

How did he know his companion was smiling?

This puzzle is for Harry Potter fans. Do you know why Tom Riddle is called Lord Voldemort?

Replace the question mark in the picture below.

Can you discover the missing number in this series?

37, 10, 82
29, 11, 47
96, 15, 87
42, ?, 15

I am the beginning of the end, and the end of time and space. I am essential to creation, and I surround every place. What am I?

By what process could you make a 'Tea-Table' into food?

"That Restaurant always remains crowded. This is the reason why nobody goes there".

Can you find a flaw in this statement?

Can you count the number of triangles in the given figure?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?