Grade: 1, Topic(s): mental number line

## Purpose

To use clues of number before and number after to identify a given number.

With the class, practice counting from 0 to 20 and then from 20 to 0. Then select a secret number but only tell children the number that comes *before* it and *after *it. After several rounds, have a child choose the secret number and call on volunteers to tell the number that comes *before* it *or* *after* it. As children are good at this, challenge them to find the number that comes *two after* or* two before*. You might say, “What comes after ______, and after that?”

Part 1 begins with identifying numbers that come *before* and *after* a number 1 to 19 using a number line. Part 2 has the *children* think of a number and give the *before *and *after *clues. The Extension moves to find the number that comes *two after* or* two before.*

I’ll choose a secret number between 1 and 19, but I’m only going to tell you the number that comes *before* it and the number that comes *after* it as clues. You try to figure out my secret number using the number line.

Examples:

- 16, 18 (secret number: 17)
- 11, 13 (secret number: 12)
- 9, 11 (secret number: 10)
- 15, 17 (secret number: 16)
- 9, 11 (secret number: 10)

*While children are enjoying their building of mastery, feel free to repeat. When children are eager for more, try Part 2.*

I’ll ask for a volunteer to think of a number between 1 and 19, but only tell the number that comes *before *it or *after *it. Everyone’s job is to figure out what the secret number is using _______’s (child’s name) clues.

Examples:

- the number
*before*is 16 (secret number: 15) - the number
*after*is 16 (secret number: 17) - the number
*before*is 10 (secret number: 9) - the number
*after*is 10 (secret number: 11)

*As always, when children seem excited for a new challenge, move on.*

Now let’s try to find the number that comes *two after* or* two before*. You might say, “What comes *after* ______, and *after* *that*?” or What comes *before* _____, and *before that*?”

Examples:

- What comes
*after*14, and*after*that? (15, 16) - What comes
*before*12, and*before*that? (11, 10) - What comes
*after*11, and*after*that? (12, 13) - What comes
*before*19, and*before*that? (18, 17)

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