**Activity 27: Number line**

**Synopsis: **This ITP generates a number line. Two markers with numbered boxes can be moved along the number line. Depending on the order of the two markers you can show the sum and difference between the two numbers and the calculation represented. You can hide and reveal the numbers in the boxes, which will also hide and reveal the respective numbers in the calculation. The maximum and minimum values on the number lines can be altered and the numbered intervals can be hidden and revealed.** **

The ITP can be used to model calculation strategies for addition and subtraction and to develop childrenâ€™s understanding of the sums and differences between positive and negative numbers. Selecting different scales on the number line and hiding and revealing the numbered intervals can support childrenâ€™s estimation skills and ability to read horizontal scales.