← Home

10 More or 10 Less

PROCEDURAL
Mathematics›Number Representation & Place Value|Ages 6—7|ID: mt_kw7xmp68rU

Mentally find 10 more or 10 less than a given two-digit number without counting

Mastery Evidence

  • Given 56, quickly say 66 is 10 more and 46 is 10 less
  • Explain that adding 10 increases the tens digit by 1
  • Answer '10 more than 73' without using fingers or counting on

Assessment Prompt

“Can [child] quickly tell you what is 10 more than 43 or 10 less than 71 — without counting up or down one at a time?”

Curriculum Standards1 alignment

1.NBT.5Common Core State Standards for Mathematics
Mentally find 10 more or 10 less

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

NBT

Prerequisites2

Show full prerequisite tree
  • One More Each Time soft

    10 more/less generalises the concept of one more/one less to tens

    • How Many in Total? hard

      Understanding 'one more/one less' requires understanding that each number represents a quantity (cardinality)

      • One-to-one counting hard

        Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'

  • The two digits of a two-digit number hard

    Mentally finding 10 more/less requires understanding that the tens digit changes

    • A Ten Is Ten Ones hard

      Understanding tens and ones place value requires the concept of 10 as a bundle

      • The teen numbers hard

        Understanding 10 as a bundle builds on understanding teen numbers as 'a ten and some ones'

        • How Many in Total? hard

          Understanding tens-and-ones composition requires cardinality — knowing numbers represent quantities

          • One-to-one counting hard

            Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'

        • Reading and writing numbers to 20 hard

          Composing/decomposing teen numbers requires reading and writing those numerals

          • How Many in Total? hard

            Reading/writing numerals 0–20 requires understanding that numerals represent quantities (cardinality)

            • One-to-one counting hard

              Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'

          • Writing digits 0-9 hard

            Writing numerals requires the motor skill of forming digits 0-9 (taught in English handwriting)

    • The teen numbers hard

      General two-digit place value extends from understanding teen number composition

      • How Many in Total? hard

        Understanding tens-and-ones composition requires cardinality — knowing numbers represent quantities

        • One-to-one counting hard

          Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'

      • Reading and writing numbers to 20 hard

        Composing/decomposing teen numbers requires reading and writing those numerals

        • How Many in Total? hard

          Reading/writing numerals 0–20 requires understanding that numerals represent quantities (cardinality)

          • One-to-one counting hard

            Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'

        • Writing digits 0-9 hard

          Writing numerals requires the motor skill of forming digits 0-9 (taught in English handwriting)

Unlocks3