Odd and even numbers

problem
Sets of numbers

Age

7 to 11

Challenge level

How many different sets of numbers with at least four members can you find in the numbers in this box?
problem
Sets of four numbers

Age

7 to 11

Challenge level

There are ten children in Becky's group. Can you find a set of numbers for each of them? Are there any other sets?
problem
Crossings

Age

7 to 11

Challenge level

In this problem we are looking at sets of parallel sticks that cross each other. What is the least number of crossings you can make? And the greatest?
game

Part the piles

Age

7 to 11

Challenge level

Try to stop your opponent from being able to split the piles of counters into unequal numbers. Can you find a strategy?
problem
Seven flipped

Age

7 to 11

Challenge level

Investigate the smallest number of moves it takes to turn these mats upside-down if you can only turn exactly three at a time.
problem
Curious number

Age

7 to 11

Challenge level

Can you order the digits from 1-3 to make a number which is divisible by 3 so when the last digit is removed it becomes a 2-figure number divisible by 2, and so on?
problem
Square subtraction

Age

7 to 11

Challenge level

Look at what happens when you take a number, square it and subtract your answer. What kind of number do you get? Can you prove it?
problem
Magic crosses

Age

7 to 14

Challenge level

Can you find examples of magic crosses? Can you find all the possibilities?
problem
Neighbourly addition

Age

7 to 14

Challenge level

I added together some of my neighbours' house numbers. Can you explain the patterns I noticed?
problem
Picturing square numbers

Age

11 to 14

Challenge level

Square numbers can be represented as the sum of consecutive odd numbers. What is the sum of 1 + 3 + ..... + 149 + 151 + 153?