1
Break and add
Joyful Mathematics: Chapter 6
GoalBreak a number into ten and ones to add it.
New words
break · split a number into partsten and ones · a number in two partsadd the ones · add the small parts first
Explanation
We can break a number to add it. Look at 14 + 5. Break 14 into 10 and 4. Add the ones: 4 + 5 = 9. Now add the ten: 10 + 9 = 19. So 14 + 5 = 19. The frames show the ten, the 4 and the 5.
Worked examples
11 + 7: break 11 into 10 and 1. 1 + 7 = 8. 10 + 8 = 18.
12 + 3: break 12 into 10 and 2. 2 + 3 = 5. 10 + 5 = 15.
13 + 4: break 13 into 10 and 3. 3 + 4 = 7. 10 + 7 = 17.
Class activity
Ten and tell. The grown-up says a sum such as 12 + 5. The child says: "Ten, and 2 plus 5 is 7. So 17." Practise with five sums. Keep one number between 11 and 15 and the other between 1 and 5.
Practice
1
How many dots altogether?
18.
2
How many dots altogether?
19.
3
What is 10 + 6 + 2?
18.
4
Break 14 + 3: 10 + ___ + 3. What is the answer?
4. 10 + 4 + 3: 4 and 3 make 7, so the answer is 17.
5
What is 17 + 2?
19.