Which set of numbers that add to 100 have the largest product?

Think of two whole numbers under 10, and follow the steps. I can work out both your numbers very quickly. How?

What is the greatest number of counters you can place on the grid below without four of them lying at the corners of a square?

One quarter of these coins are heads but when I turn over two coins, one third are heads. How many coins are there?

There are lots of different methods to find out what the shapes are worth - how many can you find?

Katie had a pack of 20 cards numbered from 1 to 20. She arranged the cards into 6 unequal piles where each pile added to the same total. What was the total and how could this be done?

Amy has a box containing domino pieces but she does not think it is a complete set. Which of her domino pieces are missing?

48 is called an abundant number because it is less than the sum of its factors (without itself). Can you find some more abundant numbers?

On a digital 24 hour clock, at certain times, all the digits are consecutive. How many times like this are there between midnight and 7 a.m.?

How many winning lines can you make in a three-dimensional version of noughts and crosses?