Strategies to Add & Subtract within 20 (Make a 10 & Doubles Facts)

You break that number into two parts. The sum of the two parts is the original number.

Answers will vary. Sum of two given numbers should add to 10.

The one in the number tells me that there is a 10. The second digit tells me how many more. 18 is 10 and 8 more.

You can move 3 counters over to the 7. 7 + 3 = 10. Then there are 5 counters left. So, it is 10 and 5 more.

The counters originally showed 7 + 8. Now they show 10 + 5 = 15.

Answers will vary. Students may make a 10 by adding 6 + 4 + 3. Students may use a doubles fact: 6 + 6 + 1.

Answers will vary. Students may make a 10 by adding 8 + 2 + 2. Students may use doubles facts and add 4 + 4 + 4.

Answers will vary. Students may say they always use one strategy or that they choose the doubles strategy if the addends are the same or 1 apart.

Answers will vary. Students may describe a counting back strategy: 14 – 4 = 10, 10 – 3 = 7. They may count on 7 + 3 = 10, 10 + 4 = 14. 3 + 4 = 7. Students may also remember that 14 and 7 are part of a doubles fact, so the difference must be 7.

Answers will vary. Students may say they always use one strategy or that they choose the count on strategy when they have to 'cross 10' when subtracting.