What a chart says, and what it holds back
Show on a big screenSomeone shows a chart with four slices and no numbers on it. How many picked cricket?
- A chart, four slices, no total.
- Cricket's slice: 3 of 8.
- "How many voters?" — no total.
- Total written: 40 voters.
You cannot tell. The chart shows only shares. A share is a group's part, like 3 of 8.
Rule: A chart with no numbers gives shares, not counts. Write the total beside it, and every count comes back.
The shares alone show which slice is bigger. Cricket is 3 of 8, which is under half of the votes. You cannot say how many people that is. You need the total.
One known count and its slice give the total. A 90° slice is a quarter of the circle. That is because 4 × 90° = 360°. Take 18 children in that slice. The whole circle is 4 such slices. So the total is 4 × 18 = 72 children.
Each chart has no total. Find how many people were asked.
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Try the lab to finish this lesson.