2nd Grade
Facts within 20 (Know all sums with single-digit addends.)
Development of Facts
In second grade students are expected to know all the sums with single-digit addends (such as 5 + 6, 9 + 9, 7 + 3). They begin to use a variety of strategies to solve addition or subtraction problems. A number line is a helpful tool for students to show their thinking using these strategies.
In addition to helping your child develop fluency with addition and subtraction facts, your child can begin to skip count by 2’s, 5’s, and 10’s. Using collections of small objects, encourage your child to count using groups. For example, count out groups of 2 objects, saying “2, 4, 6, 8, 10,” etc. This builds a foundation for multiplication facts, the 3rd grade expectation.
Addition and subtraction strategies you can help your child explore.
Counting on
When given an addition problem such as 3 + 8, the student begins with the larger number, 8, and counts on 3 to find 11.
When given a subtraction problem such as 11 - 8, the student begins at 8 and counts on to find the difference between 8 and 11. This “difference” is the answer to the subtraction problem.
Example: I know that 11 - 8 is the same as 8 + __ = 11. I can count 8, 9, 10, 11. 8 + 3 = 11. I added 3 more to 8 to get 11. My answer is 3.
Making a ten (addition)
When given an addition problem such as 6 + 7, the student will break apart one number, make a ten by adding this part to the other number, and then add the remaining part.
Example: I don’t know 4 + 7, but I can break apart 4 into 1 + 3. Then I think 3 + 7 = 10. I still have to add 1 more. Now I add 10 + 1 to get 11.
Making a ten (addition)
When given an addition problem such as 6 + 7, the student will break apart one number, make a ten by adding this part to the other number, and then add the remaining part.
Example: I don’t know 4 + 7, but I can break apart 4 into 1 + 3. Then I think 3 + 7 = 10. I still have to add 1 more. Now I add 10 + 1 to get 11.
Breaking apart a number leading to a ten (subtraction)
When given a subtraction problem such as 15 - 9, the student will break apart, subtract a part to find 10, and then subtract the rest of the number.
Example: I don’t know 15 - 9. I can break 9 into 5 + 4. Then I think 15 - 5 = 10. I have to subtract 4 more, so I do 10 - 4 = 6.
Knowing Doubles
Many students know doubles (such as 2 + 2, 3 + 3, 7 + 7) because they see examples of doubles in our everyday world.
Near Doubles
(Doubles + 1 and Doubles - 1)
These are facts in which one addend is one more or one less than the other addend (such as 5 +6, 7 + 8, 5 + 5). Students use doubles to help them find these facts.
- Double the smaller number and then add one.
5 + 6 = 5 + 5 + 1
- Double the larger number and then subtract one.
7 + 8 = 8 + 8 - 1
