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I’m an instructional math coach for an elementary school district. We’re having some debate about the language in the standard 1.NBT.4:
“Add within 100, including adding a 2-digit number and a 1-digit number, and adding a 2-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding 2-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.”Our question is: should students be adding a 2-digit and a 2-digit number? We understand the special circumstances of 2-digit and 1-digit, and 2-digit and multiple of ten, but does this standard ALSO include 2-digit and 2-digit (for example, 48 + 29)?
Thank you in advance for your help!
It seems like your example of 48 + 29 fits within the standard because the sum is within 100. The standard points out two specific things – adding a 2-digit and a 1-digit, and adding a 2-digit to a multiple of 10. I don’t read those as limiting, but rather as illustrating the underlying understanding of counting on by tens and ones.
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