I am an odd number. Take away a letter and I become even. What number am I?

Can you find the odd number in the following?

2716, 4135, 5321 and 7145

Who is that with a neck and no head, two arms and no hands? What is it?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

There’s a girl who has a large family. She has an equal amount of brothers and sisters, but each brother only has half as many brothers and sisters. What’s the correct amount of brothers and sisters?

What is the centre of gravity?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

Can you count the number of quadrilaterals in the picture below?

You see a mathematical expression in the picture. Can you think of a movie that this expression refers to?

When is the top of a mountain similar to a savings account?