How to work out a percentage of an amount

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A one-minute video showing you how to work out a percentage of an amount using bar models.

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STEP 1 - DRAW TWO BARS: Write out the problem and circle the key information. Here it is the percentage you want to find, 20%, and the weight of the chocolate, 70 g...
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…then draw two parallel bars and label the top one with the weight of the chocolate.
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STEP 2 - MARK % ON LOWER: On the bottom bar, label the right end 100%. Estimate by eye where 20% is, mark it with a vertical line and colour it in...
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...then draw a line directly above it on the top bar and colour that part in too. Put a question mark under it. This is the amount you need to find, 20% of 70 g. Can you estimate, just by eye, roughly how much it will be?
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STEP 3 - CONVERT TO DECIMAL: Convert the percentages to decimals by dividing by 100. A quick way to do it in your head is to think of per cent is as pence in the pound, so 20% is 0.20, and 100% is 1.
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STEP 4 - MULTIPLY BY DECIMAL: Write down the calculation: the weight of the chocolate multiplied by the decimal. Before you use a calculator, can you estimate what the answer will be, or think of a quick way to do it in your head?
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Use a calculator to check. Then write the answer where the question mark was. Don’t forget the right units – here it’s a weight so it’s ‘g’ for grams. You’ve done it!
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When you've worked out the answer, think about what it means in context. Can you visualise it?