Material Type:
Activity/Lab, Assessment, Formative Assessment
Lower Primary
  • 10
  • 100
  • Add
  • Addition
  • CL5Assessment
  • Cluster 5
  • Count
  • Hundred
  • Mentally
  • SKIP
  • Subtract
  • Subtraction
  • Ten
  • Unit 5
    Creative Commons Attribution
    Media Formats:
    Downloadable docs

    Education Standards

    T4T Mentally Add 10 & 100 (NBT.8)

    T4T Mentally Add 10 & 100 (NBT.8)


    This resource is from Tools4NCTeachers. 

    This file contains a set of 6 tasks (including scoring rubric and student recording sheet).  The tasks may be used for instruction or assessment. 

    Remix this resource to include student work samples or addtional tasks.

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    Add and Subtract 10


    Numbers and Operations in Base Ten


    Use place value understanding and properties of operations.


    2.NBT.8 Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.


    Paper, pencil, student form


    Give students a copy of the student form.  Say: Today I want you to mentally add and subtract 10 to numbers.  Write the answer to each equation on the lines.  When you finish solving those equations, you will write a sentence or two to explain your strategy for adding 10 mentally.  Lastly, you will write a sentence or two to explain your strategy for subtracting 10 mentally. 

    Teacher Note:  If you see a student struggling from the beginning, offer a hundred board or manipulatives to help him/her work through the task.



    Continuum of Understanding

    Not Yet Proficient

    Needs prerequisite concepts adding 10 or subtracting 10 to a given number, 0-100

    • Student is unable to mentally solve any equations correctly.

    Checklist for teacher to identify mastery of standard:

    • Student adds 10 in all 4 addition equations.
    • Student subtracts 10 in all 4 subtraction equations.
    • Student is able to explain a strategy to solve the addition and subtraction equations.


    • Student answers addition equations correctly but cannot solve the subtraction equations.
    • Student answers subtraction equations correctly but cannot solve the addition equations.
    • Student answers some equations correctly and explains a mental strategy for adding and subtracting.
    • Student answers all 8 equations correctly, but does not describe mental strategies for solving them. (orally or written)

    Meets Expectation

    • Student answers all equations correctly and describes a mental strategy for adding and subtracting 10 (orally or written).



    Standards for Mathematical Practice

    1.  Make sense and persevere in solving problems.

    2.  Reason abstractly and quantitatively.

    3.  Construct viable arguments and critique the reasoning of others.

    4.  Model with mathematics.

    5.  Use appropriate tools strategically.

    6.  Attend to precision.

    7.  Look for and make use of structure.

    8.  Look for and express regularity in repeated reasoning.


    Mentally add 10.


    135 + 10 = _____                                     


    692 + 10 = _____                                     


    550 + 10 = _____


    190 + 10 = _____                                    


    Explain your strategy for adding 10 to a number.





    Mentally subtract 10.


    178 - 10 = _____


    760 - 10 = _____


    336 - 10 = _____


    225 - 10 = _____


    Explain your strategy for subtracting 10 from a number.