Mathematics (2019) Grade(s): 1

MA19.1.14

Given a two-digit number, mentally find 10 more or 10 less than the number without having to count, and explain the reasoning used.

Unpacked Content

Knowledge

Students know:
  • how to mentally find 10 more or 10 less of a two digit number and explain reasoning.
  • place value vocabulary: tens, ones.

Skills

Students are able to:
  • mentally add or subtract 10 from a number in the range from 1
  • 100.
  • Explain their reasoning using place value understanding and patterns.

Understanding

Students understand that:
  • patterns in the place value system can be used to mentally compute sums and differences.

Vocabulary

  • Ten more
  • Ten less
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