Unmultiply is a game of quick estimation. You need to find two numbers that multiply together to something close to the given target - fast! 10 levels with a high scores table.

Powers of numbers behave in surprising ways. Take a look at some of these and try to explain why they are true.

These pictures and answers leave the viewer with the problem "What is the Question". Can you give the question and how the answer follows?

Can you convince me of each of the following: If a square number is multiplied by a square number the product is ALWAYS a square number...

Each clue number in this sudoku is the product of the two numbers in adjacent cells.

This Sudoku puzzle can be solved with the help of small clue-numbers on the border lines between pairs of neighbouring squares of the grid.

What is the largest number which, when divided into 1905, 2587, 3951, 7020 and 8725 in turn, leaves the same remainder each time?

How many zeros are there at the end of the number which is the product of first hundred positive integers?

Vedic Sutra is one of many ancient Indian sutras which involves a cross subtraction method. Can you give a good explanation of WHY it works?

Evaluate these powers of 67. What do you notice? Can you convince someone what the answer would be to (a million sixes followed by a 7) squared?

Find a great variety of ways of asking questions which make 8.