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Hi Libby, I am going to look at a circle graph where the percentages are different. First notice that the four percentages I have add to 100% as is the case with the five percentages in your question. This means that the wedges in the circle graph cover the entire circle. All the way around the circle is 360^{o} and the 50% wedge goes half way around so the central angle for the 50% wedge is 50% of 360^{o} which is 1/2 × 360^{o} = 180^{o}. The 40% wedge uses 40% of 360^{o} as its central angle and hence the angle is 40% of 360^{o} or 40/100 × 360 = 144^{o}. Likewise the central angle for each of the two remaining wedges is 5% of 360^{o} or 18^{o}. I hope this helps,
 


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