54
Adding across ten (practice)
Textbook Part 2, pp. 28–29
GoalAdd across ten quickly and correctly; show it on a number line.
New words
number line · sonlar nurijump · sakrashpigeon · kaptar
Explanation
On a number line, adding across ten takes two jumps: the first jump to 10, the second for the rest. 7 + 6: 7 → 10 (3 steps), 10 → 13 (3 steps). When adding three numbers, look first for a pair that makes 10.
Worked examples
Vali counted 8 white and 9 grey pigeons: 8 + 9 = 8 + 2 + 7 = 17.
Salim saw 6 poplars, 7 maples and 5 firs: 6 + 7 + 5 = 18.
Class activity
A 0–20 number line on the floor. A child says the sum and moves in two jumps (to 10, then beyond).
Practice
1
8 + 9 = ?
17
2
7 + 8 = ?
15
3
4 + 7 + 6 = ?
17
4
Umid watered every 2nd tree and Zulfiya every 3rd. Of 6 trees, which got no water?
Trees 1 and 5