Question

A recipe calls for $1.2$ cups of oil. How many litres of oil is this?

Answer 1

Hint: We should at first write the definition of a metric cup, which is \[1\text{ cup }=\text{ }0.25\text{ litre}\] . From this relation, we find the corresponding value of $1.2$ cups.

Complete step-by-step solution:
What is a cup? The first thing that comes to our mind when we hear of the word “cup” is a cup of tea. But, in technical terms, it is not the exact definition of cup. It is a unit to measure volume, and had been invented for cooking purposes mostly. In the earlier years of inventions, a unit of cooking ingredient volume measurement had to be found out. The conventional units like the litre, millilitres or the cubic metre were either too big or too small for the purpose of cooking. So, an accordingly suitable unit was invented, which was named the cup.
Now, there are various cup units, that is there are cup units under various unit systems. For example, there is the US cup, the metric cup, the Canadian cup, the Japanese cup and the Russian cup. This nomenclature seems more to be regional than any unit system. The US cup and the metric cup are however the most widely used across the world. In this problem, we assume the cup to be metric and proceed.
By definition,
\[1\text{ cup }=\text{ }0.25\text{ litre}\]
So,
$\begin{align}
  & \Rightarrow 1.2\text{ cups }=\text{ }\left( 1.2\times 0.25 \right)\text{ litre} \\
 & \Rightarrow 1.2\text{ cups }=\text{ }0.3\text{ litre} \\
\end{align}$
Therefore, we can conclude that $1.2\text{ cups}$ is equivalent to $0.3\text{ litre}$.

Note: To solve these types of problems, we should be well aware of the various units other than the conventional ones. Without the extra unit knowledge, we will not be able to solve this. Also, if nothing is mentioned as such of the type of cup, we should assume it to be a metric cup. Moreover, the calculations must be done flawlessly.