Videos and songs to help Kindergarten and Grade 1 kids learn to add and subtract within 20, demonstrating fluency for addition and subtraction within 10 by creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).
Common Core: 1.OA.6
- I can add and subtract within 10 easily.
- I can add and subtract by creating equivalent sums from doubles. (e.g., adding 8 + 9 by creating the known equivalent 8 + 8 + 1 = 16 + 1 = 17)
Add Doubles Strategy,
More Lessons for Grade 1,
Common Core for Grade 1
Mental Math Strategies: Use Known Equivalent Sums
This video explains how to use mental strategies to add within 20 using known sums to solve unknown sums. This is one of the strategies suggested in the Common Core State Standards for Mathematics, 1.OA.6 and 2.OA.2.
With practice, this strategy can help students gain fluency when adding within 20. Eventually students will memorize these facts, which is expected by the end of grade 2.
6 + 7 = 6 + 6 + 1 = 12 + 1 = 13
6 + 8 = 6 + 6 + 2 = 12 + 2 = 14
9 + 7 = 7 + 2 + 7 = 14 + 2 = 16
Double Plus 1 Addition Facts
"Double plus one" facts are based on knowing doubles first, then just counting on one. This allows students to answer questions in which two adjacent numbers, such as 4 and 5, are added: Double 4 = 8, so 4 + 5 = 8 + 1 = 9.
Doubles Plus One
This video provides an example of a math strategy called Doubles Plus 1 or Near Doubles to help students with math facts.
Doubles and Near Doubles
Addition Strategy (Doubles).
Math - Doubles Strategies
This video describes using the doubles strategies for addition doubles plus 1 and doubles minis 1.
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