Succeed with maths – Part 2
Succeed with maths – Part 2

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Succeed with maths – Part 2

3.1 Formulas in cooking

The time to cook a fresh chicken depends on its mass (commonly called weight in everyday language), as given by the following formula:

cooking time in minutes equation left hand side equals right hand side 15 postfix plus times mass in grams divided by 500 multiplication 25

Roughly how long will a chicken with a mass of 2.2 kg take to cook?

To use the formula, you need to substitute the mass of the chicken into the right side of the formula and then work out the resulting calculation. However, the formula asks for the mass in grams, so the first step is to convert 2.2 kilograms (kg) into grams (g).

Since there are 1000 g in 1 kg, mass in grams equals 2.2 kg equation left hand side equals right hand side 2.2 multiplication 1000 g equals 2200 g

Substituting 2200 for the ‘mass in grams’ in the formula gives:

cooking time in minutes equation left hand side equals right hand side 15 postfix plus times 2200 divided by 500 multiplication 25

Following the BEDMAS rules, the multiplication and division must be carried out first, which gives:

cooking time in minutes equation sequence equals 15 plus 110 equals 125

(If you are unsure about what BEDMAS is, you can find out more in Succeed with maths – part 1 [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] .)

So the cooking time would be about 125 minutes, or 2 hours and 5 minutes.

Now use the same formula for a different sized chicken in the next activity. Remember to check carefully what units of mass are required.

Activity 6 A smaller bird

Timing: Allow approximately 5 minutes

How long would it take to cook a chicken with a mass of 1.6 kg?

Answer

First, convert 1.6 kg into grams, since the formula requires the mass in grams.

one kg equals 1000 g

So, mass in grams equals 1.6 kg prefix multiplication of 1000 equals 1600 g

Substituting this value into the formula gives:

cooking time in minutes equation sequence equals 15 plus 1600 divided by 500 multiplication 25 equals 95 minutes

The chicken would take about 95 minutes, or 1 hour and 35 minutes to cook.

The next example is an application from health care.

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