TEACHER GUIDE TO CLARIFICATION
Add and subtract within 20.
1.OA.6 Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on, making ten (e.g., 8 + 6 = 8 + 2 + 4 = 14), decomposing a number leading to a ten
(e.g., 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9), using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 – 8 = 4), and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).
Make Ten: when one of the addends is a 7, 8, or 9, make it a ten by taking from the other addend. When the numbers are larger, adding with a ten is easier and more efficient then counting on.
Example: 8 + 4 = 12 think: 8 + 4 = 8 + 2 + 2
Example: 8 + 7 = ____
Making 10 and Decomposing a Number
I know that 8 plus 2 is 10, so I decomposed (broke)
the 7 up into a 2 and 5. First I added 8 and 2 to get
10, and then added the 5 to get 15. 8 + 7 = (8 + 2) + 5 = 10 + 5 = 15
Creating an Easier Problem with Known Sums
Known Sums. I know 8 is 7 + 1. I also know that 7 and 7 equal 14 and then I added 1
more to get 15.
8 + 7 = (7 + 7) + 1 = 15
Example: 14 – 6 = ___
Decomposing the Number You Subtract
I know that 14 minus 4 is 10 so I broke the 6 up into a 4 and a 2. 14 minus 4
is 10. Then I take away 2 more to get 8.
14 – 6 = (14 – 14) – 2 = 10 – 2 = 8
Relationship between Addition and Subtraction
6 plus __ is 14. I know that 6 plus 8 is 14, so that means that
14 minus 6 is 8.
6 + 8 = 14 so 14 – 6 = 8
Kansas Association of Teachers of Mathematics (KATM) Flipbooks.
Coherence and Connections: Need to Know
Students need to see the structure (MP 7) of how 1.OA.6 and MAKING A TEN relate to place value understanding.
If you can’t count on BY 10 FROM ANY number this will not be an efficient strategy.
1.OA.6 is strongly connected to all the standards in this domain. It focuses on students being able to fluently add and substract numbers to 10.
Adding fluently refers to knowledge of procedures, knowledge of when and how to use
them appropriately, and skill in performing them flexibly, accurately, and efficiently.
Throughout grades K-4, students should have numerous experiences and develop
expertise with breaking numbers apart, DECOMPOSING, and putting them back
together in smart ways.
Efficient strategies (particularly ones based on place value, making ten or getting to the
nearest ten) should be used when “mental math” is possible.
The traditional algorithms for addition and subtraction are expected to be used
beginning part of the way through grade 3 and mastered by the end of grade 4.
Standards 1.OA.6 and 1.NBT.5 are such starting places and are essential building blocks for all of the arithmetic of grade 1. They must therefore be given ample attention early in the year. Though often notated on paper, 1.OA.6 and 1.NBT.5 as well as 1.NBT.6 are essentially mental arithmetic knowledge and reasoning.
The study of word problems in grade 1 (1.OA.1, 1.OA.2) can be coordinated with students’ growing proficiency with addition and subtraction within 20 (1.OA.6) and their growing proficiency with multi-digit addition and subtraction (1.NBT).
PARCC Draft Model Content Frameworks: Mathematics Grades K-2
Alternatives to timed-tests include interviews and observations of playing games
Remember the study of word problems can be coordinated with this standard.
Also check out Student Achievement Partners Coherence Map
1. Have students create their own word problems for the two ten frames. Have them solve the problem and show their thinking with words, numbers and pictures.
Have students share their problems with their classmates and sort who solved by using the making a ten strategy.
My Addition Story Problem
Written and Illustrated by ............................
Write a number sentence that matches this story
2. Tori went to the market and bought 3 apples, 8 bananas, and 7 oranges to make a fruit salad. How many pieces of fruits did she buy? Explain the strategy you use to solve the problem with pictures, words, and equation.
3. Add 2, 5, and 8 using the make a ten strategy.
4. Rexi solved 9 + 8. Her work is below. Do you agree with her thinking?
1 + 7
9 + 8 = 9 + 1 + 7
Inside Mathematics Problem of the Month
Student Achievement Partners Task
National Library of Virtual Manipulatives