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Mentally adding hundreds to 3-digit numbers

PROCEDURAL
Mathematics›Addition & Subtraction|Ages 7—8|ID: mt_xPqczp7zPX

Mentally add and subtract a three-digit number and hundreds

Mastery Evidence

  • Calculate 345 + 200 mentally
  • Calculate 762 − 400 mentally
  • Explain that only the hundreds digit changes

Assessment Prompt

“Can [child] quickly work out '342 + 200' or '756 − 300' in their head — knowing that only the hundreds digit changes?”

Curriculum Standards1 alignment

Ma/KS2/Y3/AS/1cThe national curriculum in England
Mental addition/subtraction (hundreds)

add and subtract numbers mentally, including: a three-digit number and hundreds

Mathematics · Key Stage 2

Prerequisites2

Show full prerequisite tree
  • The three digits of a three-digit number hard

    Mental add/sub of hundreds requires three-digit PV

    • A Hundred Is Ten Tens hard

      Three-digit place value requires understanding 100 as a unit

      • A Ten Is Ten Ones hard

        100 as ten tens extends understanding of 10 as ten ones

        • 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 two digits of a two-digit number hard

        Must understand two-digit place value before extending to hundreds

        • 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)

    • The two digits of a two-digit number hard

      Three-digit PV extends two-digit PV (tens and ones)

      • 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)

  • 10 or 100 More or Less hard

    Extends finding 100 more/less to adding arbitrary multiples of 100

    • The three digits of a three-digit number hard

      Requires three-digit place value to understand which digit changes

      • A Hundred Is Ten Tens hard

        Three-digit place value requires understanding 100 as a unit

        • A Ten Is Ten Ones hard

          100 as ten tens extends understanding of 10 as ten ones

          • 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 two digits of a two-digit number hard

          Must understand two-digit place value before extending to hundreds

          • 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)

      • The two digits of a two-digit number hard

        Three-digit PV extends two-digit PV (tens and ones)

        • 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)

    • 10 More or 10 Less hard

      Finding 10/100 more/less within 1000 extends finding 10 more/less of two-digit numbers

      • 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)

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