Percentages in statistics and probability
Write the result of a survey as a percentage, find a percentage from the angle of a pie sector, draw a percentage pie and write a probability as a percentage.
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Guide
per cent means "out of a hundred". If 14 of 40 people choose football, their share is 1440 and 1440 = 35100. So 35 per cent.
In a survey table we add a "percent" row: divide each count by the total and multiply by 100. The percentages add up to 100.
In a pie chart the whole circle is 360 degrees and 100 per cent. A sector of 90 degrees is 90360 of the circle, which is 25 per cent. For a circle of 20 equal parts, each part is 5 per cent.
A probability can also be written as a percentage. If 5 of 20 marbles are red, the probability of red is 520 = 25100, which is 25 per cent.
To find a percentage of an amount, turn the percentage into a fraction and multiply by the amount: 75 per cent of 1200 is 75100 × 1200. A common mistake: writing the percentage itself instead of the number.