Negative numbers in real life

Hello, and welcome to Myriora Maths! Negative numbers aren't just for maths lessons. You find them on thermometers, in bank accounts, and even in lifts! Let's see how they work in real life.

In the morning, it's negative four degrees. By lunchtime, it's six degrees. How much warmer is it? Count up to zero first: that's four degrees. Then from zero up to six: six more. That's ten degrees warmer altogether!

And the other way. It's three degrees, and then the temperature falls by eight degrees. Three steps down gets you to zero, and five more gets you to negative five.

Now money. You have twenty pounds in the bank, and you spend thirty-five pounds. Your balance is now negative fifteen pounds. That means you owe the bank fifteen pounds! A negative balance is called being overdrawn.

In a tall building, the ground floor is often called zero. The car park is underground, at floor negative two. You go from the car park up to floor five. How many floors is that? Two floors up to the ground, and five more: seven floors!

Let's try one together. A fish swims three metres below the sea. A bird flies five metres above it. How far apart are they? Say it out loud!

Three metres up to the sea, and five more up to the bird: eight metres apart!

Here's a question that catches lots of people. It's negative two degrees at night, and nine degrees in the day. What's the difference? Some people say seven, because they do nine take away two. But you have to count across zero: two, and then nine more, makes eleven!

Your turn! At night it was negative seven degrees. In the day it was five degrees. How many degrees warmer was the day? Pick the right card. You've got twenty seconds, or pause the video. Go!

Time's up! From negative seven up to zero is seven degrees. Then five more, up to five. Seven add five is twelve degrees!

Quick review. On a thermometer, count across zero to find the difference. A negative bank balance means you owe money. Below the ground floor, lifts go to negative floors. And for any difference across zero, count to zero first, then on. See you next time!