Explaining, convincing and proving

In this interactivity each fruit has a hidden value. Can you deduce what each one is worth?

Can you use the clues to complete these 5 by 5 Mathematical Sudokus?

How much can you read into a T-shirt?

Draw some angles inside a rectangle. What do you notice? Can you prove it?

If it takes four men one day to build a wall, how long does it take 60,000 men to build a similar wall?

Play the divisibility game to create numbers in which the first two digits make a number divisible by 2, the first three digits make a number divisible by 3...

Identical squares of side one unit contain some circles shaded blue. In which of the four examples is the shaded area greatest?

My two digit number is special because adding the sum of its digits to the product of its digits gives me my original number. What could my number be?

It's easy to work out the areas of most squares that we meet, but what if they were tilted?