# Question Video: Using Data to Calculate Percentage and Determine the Effectiveness of the Combined Contraceptive Pill Biology

1,500 women take the combined contraceptive pill. 7 of them have unexpected pregnancies. How effective is the pill? Give your answer as a percentage to one decimal place.

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### Video Transcript

1500 women take the combined contraceptive pill. Seven of them have unexpected pregnancies. How effective is the pill? Give your answer as a percentage to one decimal place.

This question is asking us about the percentage of the 1500 women who did not have unexpected pregnancies while taking the combined contraceptive pill. It’s helpful to try to represent this problem visually. The orange circle represents all 1500 women who took the combined contraceptive pill. We’ll remove this slice in pink, which represents the seven unexpected pregnancies.

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. So, first, we’ll subtract seven from 1500, which will give us 1493. This is the number of women who did not experience unexpected pregnancies while taking the combined contraceptive pill.

Next, we need to convert this number to a percentage. 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. And we get 99.533 continuous percent. In the question, they asked for the percentage to one decimal place. Based on our calculations, we can conclude that the combined contraceptive pill is 99.5 percent effective.