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Converting units of measurement using given conversion factors

Cooking conversions

In recipes used for cooking and baking we often find the measurements for the ingredients required in cups, teaspoons and tablespoons. Measuring cups and spoons come in standard sizes, and are common in the kitchen and in recipes because they are quick and simple to use. It's very easy to measure out a quantity of baking powder in a measuring spoon, for example - much quicker than it would be weighing it on a scale.

The pictures below are examples of measuring spoons and cups. Notice that there are half and quarter cups and spoons. This is to make it easy to accurately measure out the different quantities that are most commonly used in recipes. If you have a full set of cups (in all the different sizes), and need to measure \(\frac{\text{1}}{\text{2}}\) a cup of oil, for example, you don't have to fill a whole cup half way to the top (which is an approximation, at best). You can simply use the half measuring cup and fill it to the top.

Figure 1: Measuring spoons
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Figure 2: Measuring cups
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Sometimes recipes also call for “heaped” or “rounded” teaspoons, for example. This simply means that the substance in the spoon does not have to be levelled flat, in line with the top of the spoon - there can be a bit extra “heaped” on top of the quantity in the measuring spoon.

Figure 3: A heaped teaspoon of flour
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Figure 4: A heaped cup of flour
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If you don't have measuring spoons and cups, you can use everyday household objects to approximate the same quantity of ingredients. For example, a small tea cup is roughly the same size as a measuring cup and a heaped, normal-sized spoon is about the same quantity as a measuring tablespoon. When following a recipe though, it is important to be as accurate as possible with your measurements, so using these rough approximations is often not suitable.

The quantities that measuring cups and spoons hold can be converted to volume units (like ml and \(\ell\)) which is often useful, depending on what baking and cooking equipment you're using. For example, a recipe might call for 2 cups of mealie meal. If you don't have measuring cups but do have a measuring jug that measures ml, but know how to convert cups to ml, you can still measure out the mealie meal.

It is also useful to know how to convert between these units when you are making a larger quantity of food than a recipe is designed to produce, and you need to keep the proportions between ingredients the same.

The recipe extract below gives an example of the kinds of cooking measurements you may find:

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The following table shows some of the conversions used in cooking:

Table 1

Conversions for cooking and baking

1 cup = 250 ml

1 tablespoon (tbsp) = 15 ml

1 teaspoon (tsp) = 5 ml

Note:

you will be given these conversions in assessments.

Example 1: Converting units for cooking

Question

Convert the following units. Remember to show all of your calculations.

  1. Mbali needs 3 cups of flour to bake a cake. How many ml of flour does she need?
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  2. How much is 1250 ml of milk, in cups?
  3. Ruth has 45 ml of sugar. How many tbsp of sugar does she have?
  4. Convert 5 tbsp of oil into ml.
  5. Ayanda needs to take 20 ml of cough syrup in the evening. How many teaspoons must she take?
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  6. Andile needs to use 6 tsp of fruit juice concentrate to make a glass of juice. How many millilitres of concentrate does he need?
  7. Convert 530 ml of mealie meal into cups and tbsp.
  8. Eric made 3 cups and 5 tbsp of vegetable soup for lunch. How many ml of soup does he have?
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Answer

  1. \[\begin{align*} \text{1} \text{ cup} &= \text{250}\text{ ml}\\ \text{3} \text{ cups} \times \text{250}\text{ ml} &= \text{750}\text{ ml} \end{align*}\]
  2. \[\begin{align*} \text{1} \text{ cup} &= \text{250}\text{ ml}\\ \frac{\text{1250}\text{ ml}}{\text{250}} &= \text{5} \text{ cups} \end{align*}\]
  3. \[\begin{align*} \text{1} \text{ tbsp} &= \text{15}\text{ ml}\\ \frac{\text{45}\text{ ml}}{\text{15}\text{ ml}} &= \text{3} \text{ tbsp} \end{align*}\]
  4. \[\begin{align*} \text{1}\text{ tbsp} &= \text{15}\text{ ml}\\ \text{5} \text{ tbsp} \times \text{15}\text{ ml} &= \text{75}\text{ ml} \end{align*}\]
  5. \[\begin{align*} \text{1} \text{ tsp} &= \text{5}\text{ ml}\\ \frac{\text{20}\text{ ml}}{\text{5}} &= \text{4} \text{ tsp} \end{align*}\]
  6. \[\begin{align*} \text{1} \text{ tsp} &= \text{5}\text{ ml}\\ \text{6} \text{ tsp} \times \text{5}\text{ ml} & = \text{30}\text{ ml} \end{align*}\]
  7. When you have to convert into two units of measurement always start by dividing with the capacity of the biggest one, in this case 250 ml:
    \[\begin{align*} \text{1} \text{ cup} &= \text{250}\text{ ml}\\ \frac{\text{530}\text{ ml}}{\text{250}\text{ ml}} &= \text{2,12} \text{ cups} \end{align*}\]
    Determine the remainder in ml:
    \[\begin{align*} \text{2} \times \text{250}\text{ ml} &= \text{500}\text{ ml}\\ \text{530}\text{ ml} - \text{500}\text{ ml} &= \text{30}\text{ ml} \end{align*}\]
    Divide the remainder by the second (small) unit:
    \[\begin{align*} \text{1} \text{ tbsp} &=\text{15}\text{ ml}\\ \frac{\text{30}\text{ ml}}{\text{15}\text{ ml}} &= \text{2} \text{ tbsp} \end{align*}\]
    Write down the combined answer:
    530 ml = 2 cups and 2 tbsp
  8. Multiply each measurement by its conversion factor:
    \[\begin{align*} \text{1} \text{ cup} &= \text{250}\text{ ml}\\ \text{So }\text{3} \times \text{250}\text{ ml} &= \text{750}\text{ ml}\\ \text{1} \text{ tbsp} &= \text{15}\text{ ml}\\ \text{So }\text{5} \times \text{15}\text{ ml} &= \text{75}\text{ ml} \end{align*}\]
    Add the answers together to determine the total:
    750 ml + 75 ml = 825 ml

Exercise 1: Converting units for cooking

Alex needs to cook 10 cups of rice. How many ml of rice must he cook?

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2500 ml

A group of friends has 1500 ml of orange soda. How many cups of orange soda is this?

6 cups

Convert 90 ml of curry powder into tablespoons.

6 tbsp

What is 4 tbsp of baking powder, measured in ml?

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60 ml

A bottle contains 85 ml of medicine. How many teaspoons is this?

17 tsp

Convert 7 tsp of cooking oil into ml.

35 ml

Convert 1060 ml of fruit juice into cups and tbsp.

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4 cups and 4 tbsp

How much is 4 cups and 6 tbsp of flour, converted into ml?

1090 ml