The purpose of this activity is to engage students in generalising the difference between two sequential counting numbers, in context.

In readiness for this problem, the students should have familiarity with each of the following components of mathematics. The problem may be solved with different combinations of these components.

- apply counting-all strategies
- continue sequential patterns and number patterns based on 1s
- know the result of adding 1 to a given counting number
- Compare two sequential counting numbers to find the difference

This activity may be carried out with guidance, or by allowing the student to follow their own set of instructions. The approach should be chosen in sympathy with students’ skills and depth of understanding.

A bag of‘a dozen’ donuts has 12 donuts in it.

If the bag is labelled ‘a baker’s dozen’ then it has 13 in it.

Explain the difference between a dozen and a **baker’s dozen**.

### The visual approach (show more)

- The student is able to use images and/or materials to find the difference between two sequential counting numbers.

### The conceptual approach (show more)

- The student is able to use mathematical language and/or symbols to show the difference between two sequential counting numbers, in context.