A brand new Mobile Phone was on sale at 20% as a promotional offer. By what per cent must the Mobile price be increased to sell it at the original price again?

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

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

Which is the smallest number that you can write using all the vowels exactly once?

Three people enter a room and have a green or blue hat placed on their heads. They cannot see their own hat but can see the other hats.
The colour of each hat is purely random. They could all be green, blue, or any combination of green and blue.
They need to guess their own hat colour by writing it on a piece of paper, or they can write 'pass'.
They cannot communicate with each other in any way once the game starts. But they can have a strategy meeting before the game.
If at least one of them guesses correctly they win $10,000 each, but if anyone guesses incorrectly they all get nothing.
What is the best strategy?

Prove that twice of ten is the same as twice of eleven.

Rebus Puzzle Definition: A rebus is an illusion device that uses pictures to represent words or parts of words.
What does This Rebus Puzzle Identify?

What has no start, end, or centre?

What am I?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?