The little boy rolls the dice and writes down the number six. A second roll shows the number five. He writes that down too, and after a little thought can now work out that six multiplied by five is thirty. For most people this will be an easy calculation. But for a child with dyscalculia, having a visual image of the numbers is crucial to construct an answer.
People with dyscalculia, also known as number blindness, have difficulty acquiring skills with maths and numbers. They may have problems understanding simple number concepts and lack an intuitive grasp of maths.
For young children it can mean an inability to count from one to ten, to select the larger of two numbers, or to do what to others seem like simple sums. It can be highly frustrating for children who cannot understand why they can't get it right, leads to a loss of self-confidence and can even cause problems with behaviour in the classroom.
The condition is believed to affect up to 5 per cent of the population - or 2.5 million people. And yet, unlike word blindness or dyslexia, little is still known about dyscalculia. The learning difficulty is rarely present in isolation. Those who have it are usually also affected by dyslexia, or dyspraxia, which affects how the brain processes information.
Dorian Yeo has just published a manual offering teachers advice on how to help pupils. Dyscalculia Guidance was written with Professor Brian Butterworth of University College London, the UK's leading authority on the condition.
Ms Yeo says that children with dyscalculia are often only discovered when it comes to doing group work. "Often their parents know much earlier that there is something wrong, but they can't always identify what it is," she says.
While their classmates can confidently call out answers, the dyscalculic child will be confused and unable to understand what is expected of them.
One of the problems in identifying the condition, she believes, lies in the way pupils are first introduced to numbers in the classroom.
In most schools, multiplication tables are learned by rote until children can recite them by heart. However, dyscalculic children need additional help because they cannot visualise the concept of number.
At Emerson House, an independent special school in Hammersmith, west London, where Ms Yeo teaches, simple cognitive models are used to clarify reasoning. She uses cubes, beads, dice, plastic toys and coins one-to-one so pupils can visualise what they are learning.
Speaking and verbal instructions - apart from praise and encouragement - are kept to a minimum, and simple language is used so pupils understand exactly what is expected of them, without any confusion.
A pupil lines up 10 plastic fish in two sets of five. Next to each fish she is asked to place a 5p coin. "There is research to show that the concept of each item costing a certain amount is a very hard one for most children to understand, so we use the coins in a one-to-one correspondence to make it clear," says Ms Yeo. She then asks the pupil to work out, mentally, how much six fish will cost. The pupil knows that the first set of five fish will cost 25p, and she adds one from the second set to come up with the correct answer of 30p.
The grouping of numbers is crucial to helping dyscalculic children to learn because it helps them clarify quantity in their minds. So, for example, youngsters working on the five times table will group items in fives, or in six when working out the six-times table.
At Emerson House, children are taught individually or in small groups.
Typically, most children need a year or so, full or part-time, to enable them to catch up with their peers and to restore their confidence and enthusiasm for learning.
Ms Yeo adds: "I have seen, time and again, how pleased children are when they finally understand aspects of maths they previously found impossible."
Jane Emerson, who founded Emerson House with Ms Yeo 13 years ago, says:"I believe people are born with a 'maths brain', or a part of the brain that deals with numbers. Children who are dyscalculic cannot work in the abstract. I believe that children have to have those basic facts otherwise they will struggle throughout their school lives. We have to find ways of making sure they have them at their disposal."
Dyscalculia Guidance is published by nferNelson (pound;25) and can be purchased by calling 0845 6021937, or online from www.shop.granada-learning.com