NY Next Generation Math NY-2.NBT.8

Math2nd GradeUse place value understanding and properties of operations to add and subtract.

The Standard

Mentally add 10 or 100 to a given number 100-900, and mentally subtract 10 or 100 from a given number 100-900.

New York State Next Generation Mathematics Learning Standards

Teacher's field guide

What Students Need to Do: Students mentally add or subtract 10 or 100 from numbers from 100 through 900. They use place value to change the tens or hundreds while tracking any composition or decomposition.
What Mastery Looks Like: Given 368, the student states 378, 358, 468, and 268 for ten more, ten less, one hundred more, and one hundred less. The student explains which place changed.
Common Misconceptions: Students may change the ones digit when adding ten or change the tens digit when adding one hundred. They may count by ones instead of reasoning by place value.
How to Assess It: Give 594 and ask for 10 more, 10 less, 100 more, and 100 less. Require a place-value explanation for one answer.

Lesson moves

Use a hundreds chart extension and base-ten blocks to make mental jumps of 10 and 100.
Ask students what changes and what stays the same when 100 is subtracted from 726.
Play mental-jump chain by passing number cards and applying called changes of plus or minus 10 or 100.
Adjust a school inventory by one box of 10 or one case of 100 without written computation.

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