Lesson 8 of 14
Dots on a number line
Show on a big screenTen rides to school took these times. Minutes: 12, 13, 14, 15, 15, 15, 15, 17, 19, 25. Where are most of the times?
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Step 1 of 6
- A number line. Each small mark is 1 minute.
- Each ride is one dot, above its number of minutes.
- Equal readings stack. Four rides took 15 minutes.
- The ends: the fastest ride, 12, and the slowest, 25.
- The median is 15. Both middle readings are 15.
- The mean is 16. The total, 160, shared over 10 rides.
Nine of the ten rides took 12 to 19 minutes. Four took 15 minutes.
A dot plot gives each reading one dot on a number line.
Equal readings stack, one dot above another. The ends show the smallest and the largest. Crowded dots show where readings are close together.
| Minutes | 12 | 13 | 14 | 15 | 17 | 19 | 25 |
|---|---|---|---|---|---|---|---|
| Dots | 1 | 1 | 1 | 4 | 1 | 1 | 1 |
Count the dots: 1 + 1 + 1 + 4 + 1 + 1 + 1 = 10. That is one dot for each ride.
The median and the mean can be marked on the same line. The far dot at 25 moves the mean right of the median. The mean, 16, has no dot of its own.
Try the lab to finish this lesson.