WEBVTT
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1500 women take the combined contraceptive pill.
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Seven of them have unexpected pregnancies.
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How effective is the pill?
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Give your answer as a percentage to one decimal place.
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This question is asking us about the percentage of the 1500 women who did not have unexpected pregnancies while taking the combined contraceptive pill.
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It’s helpful to try to represent this problem visually.
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The orange circle represents all 1500 women who took the combined contraceptive pill.
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We’ll remove this slice in pink, which represents the seven unexpected pregnancies.
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What we’re being asked to calculate is what percentage of the circle of the original 1500 women is left after we remove the seven who had unexpected pregnancies.
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So, first, we’ll subtract seven from 1500, which will give us 1493.
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This is the number of women who did not experience unexpected pregnancies while taking the combined contraceptive pill.
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Next, we need to convert this number to a percentage.
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We’ll do that by dividing the number of women who did not have unexpected pregnancies by the total number of women who took the pill and multiplying by 100 percent.
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And we get 99.533 continuous percent.
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In the question, they asked for the percentage to one decimal place.
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Based on our calculations, we can conclude that the combined contraceptive pill is 99.5 percent effective.