In this quick KS3 maths lesson, we explore how to add and subtract negative numbers using an easy thermometer method. Perfect for Year 7 and Year 8 students who struggle with negative numbers or find number lines confusing. We break the steps down clearly so you can understand why negative numbers behave the way they do. A great maths basics refresher for students, parents, and anyone who wants to feel more confident with adding and subtracting negatives. #ks3 negative numbers, adding negative numbers, subtracting negative numbers.