Addition and subtraction

problem
Favourite

Connect Three

Age

11 to 16

Challenge level

2 out of 3

In this game the winner is the first to complete a row of three. Are some squares easier to land on than others?
problem

Alphabet Soup

Age

11 to 14

Challenge level

1 out of 3

This challenge is to make up YOUR OWN alphanumeric. Each letter represents a digit and where the same letter appears more than once it must represent the same digit each time.
problem

As Easy as 1,2,3

Age

11 to 14

Challenge level

1 out of 3

When I type a sequence of letters my calculator gives the product of all the numbers in the corresponding memories. What numbers should I store so that when I type 'ONE' it returns 1, and when I type 'TWO' it returns 2, and so on.
problem

Kids

Age

11 to 14

Challenge level

1 out of 3

Find the numbers in this sum
problem

Machines

Age

7 to 11

Challenge level

1 out of 3

What is happening at each box in these machines?
problem

Card Trick 2

Age

11 to 14

Challenge level

2 out of 3

Can you explain how this card trick works?
problem

The Patent Solution

Age

11 to 14

Challenge level

2 out of 3

A combination mechanism for a safe comprises thirty-two tumblers numbered from one to thirty-two in such a way that the numbers in each wheel total 132... Could you open the safe?
problem

Score

Age

11 to 14

Challenge level

2 out of 3

There are exactly 3 ways to add 4 odd numbers to get 10. Find all the ways of adding 8 odd numbers to get 20. To be sure of getting all the solutions you will need to be systematic. What about a total of 15 with 6 odd numbers?
problem

Calendar Calculations

Age

7 to 11

Challenge level

2 out of 3

Try adding together the dates of all the days in one week. Now multiply the first date by 7 and add 21. Can you explain what happens?
problem

Spell by Numbers

Age

7 to 11

Challenge level

2 out of 3

Can you substitute numbers for the letters in these sums?