How_To_Be_Good_At_Math

temperature Calculating with

World weather

In Sweden, the average temperature

in February is −3°C. If it’s 29°C hotter

in India, what is the temperature?

Calculating with

temperature

We can do addition and subtraction with temperatures

measured in degrees Celsius and Fahrenheit, although

we can’t do multiplication or division.

Sweden

−3°C

India

?°C

To find the answer, we simply need to

do a subtraction calculation. We know

that the result will be a negative number

because 40 is a larger number than 30.

The temperature at the base of this

mountain is 30°C. It’s 40°C colder at the

top of the mountain. Let’s work out what the

temperature is at the top.

Let’s subtract 40 from 30:

30 – 40 = −10

So, the temperature

at the top of

the mountain is

−10°C.

We can also work out the

temperature change by drawing

a number line just like this one.

Counting back four

groups of 10 on the

number line from 30°C

gives the answer −10°C.

Answer on page 319

Start at 30º

and count

back in 10s

−40°C

−30°C

−20°C

−10°C

0°C

+10°C

+20°C

+30°C

+40°C

TRY IT OUT

The scale on a thermometer

works just like the scale on

a number line.

186_187_Temperature.indd 187 29/02/2016 18:04