Idea 7of 22Builds onAn even count has a middle pair
Finding the number halfway
What is halfway between 8 and 11?
Today you'll discover
- add, then divide by 2
- why the median can be a half
Think firstPiano practice: 5, 8, 11, 14 minutes
The middle pair is 8 and 11. What number is halfway between them?
Decide first, then press Next. Find the mark halfway along the short line.
Four boxes in order: 5, 8, 11, 14. Slashes cross off 5 and 14. A short number line runs from 8 to 11 with a mark at its centre labelled median 9.5, and the working (8 + 11) ÷ 2 = 9.5. The last step shows birds counted on four mornings.
See the whole ideathe big idea and the key word, in one place
The big idea
To find the number halfway between two values, add them and divide by 2.
Two waysAdd and halve: (8 + 11) ÷ 2 = 9.5. Or count the gap: 8 to 11 is 3, half of 3 is 1.5, and 8 + 1.5 = 9.5.
Easy to get wrongAdding is only half the job. 8 + 11 = 19 is not the median; 19 ÷ 2 = 9.5 is.
Key word
- halfway point
- the number exactly as far from one value as from the other: add the two and divide by 2
Ready to use it?
- Find the median when the middle pair is far apart.