Directed Numbers: Making Sense of Negative Numbers

Imagine it's a bitter winter morning. The thermometer reads 3 °C. Overnight it drops by 7 degrees. What temperature is it now? You might feel that something strange happens when you subtract a bigger number from a smaller one — the answer goes 'below zero'. That's exactly what this lesson is about. Think about where you've seen numbers below zero in real life. A bank account overdrawn by £20? A car park on Level −2? A diver 5 metres below the surface? Jot down one example you can think of.