A ratio compares the relationship between two values. It tells us how much there is of one thing compared to another.
It is important that both quantities are in the same units, otherwise we cannot compare them with a ratio. In the example above, we are comparing one blue dot to three green dots, so a single dot can be thought of as our unit.
A ratio can express a "part to part" relationship like we saw in the dot example above. We can also describe a "part to whole relationship". For example, if we wanted to describe the ratio of green dots to all the dots, we could write it as 3:4, because there are 3 green dots and 4 dots in total.
The order that the words are written correspond to the order of the values in the ratio, so it is important that we don't jumble them around. We can also express fractions, decimals and percentages as ratios.
Write a numerical ratio for the number of circles to squares. Give your answer in the form a:b.
A ratio compares the relationship between two values. We write ratios in the form a:b which is read as "a to b".
Often we might want to compare two quantities that have different units, such as a number of minutes compared to a number of hours, a distance in kilometres to a distance in metres, a duration in days to a duration in weeks, and so on.
To compare these types of quantities, we will need to convert one of the quantities to use the same units as the other. It does not matter which one we convert, we will end up with exactly the same ratio in the end.
Write 31 minutes to 2 hours as a ratio.
To compare quantities with different units, we need to convert one of the quantities to the same units as the other. Then we can write it in the form a:b without units.