First Grade Mathematics Subtraction Up to 20

Understandings:

• The student must be able to solve addition and subtraction problems by applying the properties of operations. They must be able to explain how they solved the problem and how they know they are correct. (1.5) G
• The student must be able to use base-ten models, counters, open number lines, and strip diagrams (part-part-whole) to solve addition and subtraction word problems involving situations of putting together, taking apart, and comparing sets of less than 20. The students must be able to solve problems with the unknown in any position of the number sentence and be ready to model and explain their thinking. (1.3) B
• The student must be able to add two or more numbers together to make 10 with or without using concrete objects. Students must be able to use drawings and number sentences to represent these sums of 10. (1.3) C
• The student must be able to add two whole numbers whose sum is less than 20 and subtract related facts in a similar manner. They must be able to apply basic fact strategies, including combining or breaking apart two numbers to form a sum of ten and must be efficient in using the basic facts to solve problems arising in everyday life. (1.3) D
• The student must be able to explain in their own words the strategies they use to solve addition problems with sums less than 20 and subtraction problems of related facts. Student must be able to model their thinking using objects such as linking cubes and counters, pictorial models such as open number lines and strip diagrams, and number sentences. (1.3) E
• The student must be able to understand the meaning of an equal sign and must we able to pair equivalent expressions to make a true number sentence. They must be able to explain their reasoning and tell how they know the values on both sides of the equal sign are the same.(1.5) E
• The student must be able to determine the value of a missing number in an equation. They must be able to explain their reasoning and tell how they know the resulting value makes the number sentence true. (1.5) F

• 1.5 G(R) Apply properties of operations to add and subtract two or three numbers
• 1.5 E (S) Understand that the equal sign represents a relationship where expressions on each side of the equal sign represent the same value(s)
• 1.5 F (S) Determine the unknown whole number in an addition or subtraction equation when the unknown may be any one of the three or four terms in the equation
• 1.3 B(S) Use objects and pictorial models to solve word problems involving joining, separating, and comparing sets within 20 and unknowns as any one of the terms in the problem such as 2+4=___; 3+___=7; and 5 = ____‐3
• 1.3 C(S) Compose 10 with two or more addends with and without concrete objects
• 1.3 D(S) Apply basic fact strategies to add and subtract within 20, including making 10 and decomposing a number leading to a 10
• 1.3 E(S) Explain strategies used to solve addition and subtraction problems up to 20 using spoken words, objects, pictorial models, and number sentences

• I can compose the number 10 1.3C
• I can apply properties of operations to subtract 2 numbers 1.5G
• I can solve word problems using models using joining, separating and comparing 1.3B
• I can apply basic fact strategies to subtract within 20 1.3D
• I can explain strategies used to solve subtraction problems 1.3E
• I can balance subtraction equations (Ex: ___ - 3 = 5 OR 6 - 2 = ___ ) 1.5EF

• What are ways to think about subtraction?
• What strategies can you use while subtracting?

Vocabulary:   doubles, fact family, make 10, think addition/count on, twos, fives, tens, comparing. distance, unknown value
Previously introduced:  addition, difference, number sentence/equation, subtraction, sum, joining, separating