Sectieoverzicht
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To compare quantities of the same type we use ratios.
Example
A recipe requires 1 cup of water for every 2 cups of flour.
This means that the ratio of water to flour (in that order) is \(1:2\) or we can write the ratio as a fraction as \(\frac{1}{2}\) or \(1\) to \(2\).
Only quantities of the same kind can be compared using ratios. For example, litres with litres, miles with miles, grams with grams, cups with cups, and so on.
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Leerlingen moetenAls voltooid aanduiden
Working with ratio and rate
Some ratios can be simplified to an equivalent form. For example, \(5:10\) can be simplified to \(1:2\).
\(\frac{5}{10}=\frac{1}{2}\) by dividing the numerator and denominator by \(5\) we can simplify the fraction and rewrite the fraction as its equivalent \(1:2\).
Rate
To compare different types of quantities we use rate. An example is the speed of a car, which is measured in kilometres (km) per hour.
For example, if a car uses 2 litres of petrol to travel 40 km then we can find the amount of petrol needed for 20 km by dividing both the litres and kilometres by 2. We find that the rate is \(1:20\) so the car uses 1 l of petrol to travel 20 km.
Proportion
When ratios are equal we say they are in proportion. We use proportion to solve for unknown values in a ratio equation.
Example
To make an orange juice drink you must mix juice concentrate with water in the ratio \(1:3\). You need to make enough for an entire class and you have \(500\) ml of orange juice concentrate, how much water should you use?
You can set up the proportion equation to calculate the amount of water required:
In the next video you will learn how to apply ratio and rate to answer questions.
Try the next activity to make sure you understand how to answer questions on ratio and rate. Some of the questions in the activity include examples before the question. -
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