What Adam and Eve do not have but the rest of the people have?

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?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

What is always in front of you but can’t be seen?

Can you decipher the following common phrase?

T M C
A U O
H S M
W T E

You have to put a letter on the following to make it a meaningful word. The only challenge is that you can't use 'E'.

S E Q U E N C _

Find out a multi-digit number that if multiplied by the number 9 or any of its multiplications products (i.e. 18, 27, 36, 45,..) will result in the multiplication factor repeated (n) number of times.

The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.

Boxes are labeled but all labels are wrong!

You are allowed to open one box, pick one ball at random, see its colour and put it back into the box, without seeing the colour of the other ball.

How many such operations are necessary to correctly label the boxes?

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

How many letters are in the alphabet?