Once a basic number sense has developed for numbers up to ten, a strong 'sense of ten' needs to be developed as a foundation for both place value and mental calculations.

Marion Bond recommends that children should be allowed to use 'apparatus', so that they can physically handle the numbers involved in their calculations, for longer, or across a wider ability band,. . . .

Can you replace the letters with numbers? Is there only one solution in each case?

Find out what a Deca Tree is and then work out how many leaves there will be after the woodcutter has cut off a trunk, a branch, a twig and a leaf.

What happens when you round these three-digit numbers to the nearest 100?

A church hymn book contains 700 hymns. The numbers of the hymns are displayed by combining special small single-digit boards. What is the minimum number of small boards that is needed?

What happens when you round these numbers to the nearest whole number?

This 100 square jigsaw is written in code. It starts with 1 and ends with 100. Can you build it up?

In this 100 square, look at the green square which contains the numbers 2, 3, 12 and 13. What is the sum of the numbers that are diagonally opposite each other? What do you notice?

Can you work out some different ways to balance this equation?

Can you complete this calculation by filling in the missing numbers? In how many different ways can you do it?

Use two dice to generate two numbers with one decimal place. What happens when you round these numbers to the nearest whole number?

What two-digit numbers can you make with these two dice? What can't you make?

Can you find the chosen number from the grid using the clues?

If you put three beads onto a tens/ones abacus you could make the numbers 3, 30, 12 or 21. What numbers can be made with six beads?

In the multiplication calculation, some of the digits have been replaced by letters and others by asterisks. Can you reconstruct the original multiplication?

What do the digits in the number fifteen add up to? How many other numbers have digits with the same total but no zeros?

Have a go at balancing this equation. Can you find different ways of doing it?

Investigate the different ways these aliens count in this challenge. You could start by thinking about how each of them would write our number 7.

The Scot, John Napier, invented these strips about 400 years ago to help calculate multiplication and division. Can you work out how to use Napier's bones to find the answer to these multiplications?

Choose four different digits from 1-9 and put one in each box so that the resulting four two-digit numbers add to a total of 100.

This multiplication uses each of the digits 0 - 9 once and once only. Using the information given, can you replace the stars in the calculation with figures?

These spinners will give you the tens and unit digits of a number. Can you choose sets of numbers to collect so that you spin six numbers belonging to your sets in as few spins as possible?

How would you create the largest possible two-digit even number from the digit I've given you and one of your choice?

This is a game in which your counters move in a spiral round the snail's shell. It is about understanding tens and units.

Exploring the structure of a number square: how quickly can you put the number tiles in the right place on the grid?

Some Games That May Be Nice or Nasty for an adult and child. Use your knowledge of place value to beat your oponent.

four strategy dice games to consolidate pupils' understanding of rounding.

Investigate which numbers make these lights come on. What is the smallest number you can find that lights up all the lights?

Dicey Operations for an adult and child. Can you get close to 1000 than your partner?

This activity involves rounding four-digit numbers to the nearest thousand.

Each child in Class 3 took four numbers out of the bag. Who had made the highest even number?

This article for the young and old talks about the origins of our number system and the important role zero has to play in it.

I am less than 25. My ones digit is twice my tens digit. My digits add up to an even number.

There are six numbers written in five different scripts. Can you sort out which is which?

Lee was writing all the counting numbers from 1 to 20. She stopped for a rest after writing seventeen digits. What was the last number she wrote?

A game to be played against the computer, or in groups. Pick a 7-digit number. A random digit is generated. What must you subract to remove the digit from your number? the first to zero wins.

How many solutions can you find to this sum? Each of the different letters stands for a different number.

This article, written for teachers, looks at the different kinds of recordings encountered in Primary Mathematics lessons and the importance of not jumping to conclusions!

Which is quicker, counting up to 30 in ones or counting up to 300 in tens? Why?

Four of these clues are needed to find the chosen number on this grid and four are true but do nothing to help in finding the number. Can you sort out the clues and find the number?

There are nasty versions of this dice game but we'll start with the nice ones...

Who said that adding, subtracting, multiplying and dividing couldn't be fun?

You have a set of the digits from 0 – 9. Can you arrange these in the 5 boxes to make two-digit numbers as close to the targets as possible?

You have two sets of the digits 0 – 9. Can you arrange these in the five boxes to make four-digit numbers as close to the target numbers as possible?

Start by putting one million (1 000 000) into the display of your calculator. Can you reduce this to 7 using just the 7 key and add, subtract, multiply, divide and equals as many times as you like?