Hello,

We just completed RS E lesson 115. In it, Dr. Cotter says "To find the angle she needs to multiply the percent by 360 (and round to whole numbers)." When you do this, you do not get the central angle as listed in the text and it sums to 361 rather than 360. I talked to DS about rounding errors etc and then we did it using the fraction instead and got the numbers in the table for central angle and they summed to 360. Was the intent for DC to use the fractions rather than the percents?

Thanks,
Capt_Uhura

Capt_Uhura,

Thank you for your message. I did check with Dr. Cotter for clarification and she advised that there are two ways to solve the problem, they are as follows:

1. After finding the percents and before clearing the calculator, multiply by 360. This is the most accurate and gives the answers as stated. They do total to 360.

2. Find the percents and round to the whole number. Then reenter each rounded percent and multiply by 360. The central angles will differ slightly from what is shown, but they will total to 360.

Since the point of the problem is to turn the data into a pie chart, method 1 is simplest and most accurate. Totals not being exact frequently occurs with real data.

I hope this helps, please advise if you have any additional questions.

Make it a great day,

Cassie
Activities for Learning-RightStart™ Mathematics
Cassie@ALabacus.com
www.ALabacus.com

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