Florida B.E.S.T. MA.1.NSO.2.3

Math1st GradeDevelop an understanding of addition and subtraction operations with one- and two-digit numbers.

The Standard

Identify the number that is one more, one less, ten more and ten less than a given two-digit number.

Florida B.E.S.T. Standards for Mathematics

Teacher's field guide

What Students Need to Do: Students find nearby values by changing a two-digit number by 1 or 10. They use place value, number lines, or charts to explain which digit changes.
What Mastery Looks Like: Given 47, a student gives 48, 46, 57, and 37 and labels each relationship correctly. The student also handles decade changes, such as moving from 40 to 39.
Common Misconceptions: Students may change the wrong digit, saying 48 is ten more than 47. They may struggle across a decade, such as naming 30 instead of 29 as one less than 30.
How to Assess It: Exit ticket: For 52, write the numbers reached by moving forward 1, back 1, forward 10, and back 10. Circle the digit that changed each time.

Lesson moves

Build 34 with base-ten blocks, then add or remove one cube or one rod and record each new number.
Partners explain why adding a ten usually leaves the ones digit unchanged, using 46 and 56 as evidence.
Play Number Change: students draw a two-digit number card and a move card, then say and record the result.
Use a store count, such as 63 cans, and ask how the total changes after selling or receiving 1 or 10.

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