When to use decimals outside of maths at school?
If you were ill, and had to find out whether your temperature
was raised or not, you would have to use decimals to judge this.
(At least, if you were using Celsius you would need to use
decimals). Likewise, if you were to use cookery thermometers to
assess how "cooked" a steak or sugar syrups are.
Alternatively, when using an electronic weighing scale to weigh
out substances for which accuracy is crucial (e.g yeast, agar,
emulsifiers, a chemist weighing drugs etc...) - all substances
which must be weighed on a scale which can measure "0.001" of a
gram.
Capacity of car engines are measured in decimals - e.g 1.2 litre
engine.
If you have to calculate how much carpet you need to cover a
room - the length, width or area are very unlikely to come out as a
whole number.