Addition and subtraction

problem
How do you see it?

Age

5 to 11

Challenge level

Here are some short problems for you to try. Talk to your friends about how you work them out.
problem
Take three numbers

Age

7 to 11

Challenge level

What happens when you add three numbers together? Will your answer be odd or even? How do you know?
problem
Two numbers under the microscope

Age

5 to 7

Challenge level

This investigates one particular property of number by looking closely at an example of adding two odd numbers together.
problem
Magic letters

Age

11 to 14

Challenge level

Charlie has made a Magic V. Can you use his example to make some more? And how about Magic Ls, Ns and Ws?
problem
Some secret codes

Age

7 to 11

Challenge level

Can you follow the rule to decode the messages?
problem
More plant spaces

Age

7 to 14

Challenge level

This challenging activity involves finding different ways to distribute fifteen items among four sets, when the sets must include three, four, five and six items.
problem
Fifteen cards

Age

7 to 11

Challenge level

Can you use the information to find out which cards I have used?
problem
More children and plants

Age

7 to 14

Challenge level

This challenge extends the Plants investigation so now four or more children are involved.
problem
Summing consecutive numbers

Age

11 to 14

Challenge level

15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?
problem
Escape from the castle

Age

7 to 14

Challenge level

Skippy and Anna are locked in a room in a large castle. The key to that room, and all the other rooms, is a number. The numbers are locked away in a problem. Can you help them to get out?