Math // Number Representation & Place Value

10 More or 10 Less

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

Ages
6 to 7
Type
Method
Builds on
2 topics
Leads to
3 topics
Standards
1 code

Quick check

Can the learner quickly tell you what is 10 more than 43 or 10 less than 71 — without counting up or down one at a time?

Ask this to see whether the topic is secure.

Topic // Mastery

What mastery looks like

What a learner can do once this topic is secure.
  • 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

Topic // Map

Where this fits

What to learn first and what this topic opens up, with the reason for each link. Required links come first.
  • RequiredMust come first
  • HelpfulHelps, but not essential

Before this

2 topics
  • The two digits of a two-digit numberRequired

    Number Representation & Place Value // Ages 6 to 7

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

  • One More Each TimeHelpful

    Counting & Cardinality // Ages 4 to 6

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

You are here

10 More or 10 Less

Ages 6 to 7 // Method

Leads to

3 topics
  • Adding and subtracting tens mentallyRequired

    Addition & Subtraction // Ages 6 to 7

    Adding/subtracting tens builds on mentally finding 10 more or less

  • 10 or 100 More or LessRequired

    Number Representation & Place Value // Ages 7 to 8

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

  • Generalising PatternsHelpful

    Mathematical Thinking // Ages 6 to 7

    Mentally finding 10 more/less uses generalised repeated reasoning about place value

Topic // Research-informed

Teaching notes

From the Marble Skill Taxonomy. These notes have not been validated in classrooms, so treat them as a starting point for your own judgement.

The approach

For ages 6-7: mentally find 10 more or 10 less than a two-digit number without counting on in ones, by recognising that adding/subtracting a ten changes only the tens digit while the ones digit stays the same (10 more than 56 is 66; 10 less is 46). The core objective is reasoning plus fluency: the child should both produce the answer instantly and explain why only the tens digit changes. Concrete models (100-square vertical moves, base-ten rods) build the insight; timed recall practice consolidates it once understanding is secure. Keep examples within the two-digit range where only the tens digit changes by one.

Common misconceptions

  • Counting on in ones (56, 57, 58…66) instead of jumping a ten — no place-value shortcut.
  • Changing the ones digit as well, or changing the wrong digit (56 → 57 for '10 more').
  • Confusing 10 more with 1 more.
  • Miscounting on the 100-square by moving diagonally or the wrong direction.
  • Struggling at decade boundaries because the pattern is memorised without understanding the tens digit's role.

Useful representations

  • 100-square (vertical moves = ±10) — the canonical model
  • Base-ten tens-rods and ones-cubes (add/remove one rod)
  • 0-100 number line with hops of 10
  • Place-value chart showing only the tens digit changing
  • Gattegno chart (change the tens-row selection, keep the ones)

Teaching practices

  • Exploit the 100-square structure: +10 is one row DOWN, -10 is one row UP, in the same column — the visual makes 'ones unchanged, tens ±1' obvious.
  • Use tens-rods: add or remove exactly ONE rod and narrate that the cubes (ones) never moved.
  • Insist on the generalised explanation, not just the answer, so it becomes reasoning rather than counting.
  • Contrast with '1 more/1 less' so the child distinguishes changing the ones from changing the tens.
  • Rehearse across decade boundaries to build fluency and flag where the pattern needs care.

Activities to try

  1. 1

    The 100-square vertical jump

    Why it works: Adding or subtracting ten is always the same move — straight down or up one row — and the ones digit never moves because only a whole ten is added or removed.

    1. Point to a starting number on a 100-square (for example 56).
    2. On a 100-square numbered from the top (1-10 in the top row), to find 10 more, move straight DOWN exactly one row, staying in the same column; to find 10 less, move straight UP one row in the same column. (On a bottom-up 100-square the directions are reversed. Check which way the numbers grow on your grid.)
    3. Say the new number aloud (56 → 66 for 10 more, 56 → 46 for 10 less).
    4. Repeat the +10 jump several times to trace a straight vertical stripe down the grid: 56 → 66 → 76 → 86.
    5. Each time, name the ones digit and the tens digit and state what changed: 'the ones stayed 6, the tens went up by one.'
  2. 2

    Add or remove one ten-rod

    Why it works: Adding ten means adding a single ten-rod, which changes the tens count by one and leaves the ones completely untouched.

    1. Lay out a two-digit number with base-ten tens-rods and ones-cubes (for example 5 rods and 6 cubes for 56).
    2. To add 10, place exactly ONE more rod; to subtract 10, take exactly ONE rod away.
    3. Watch the ones-cubes the whole time and say aloud that they did not move.
    4. Read the new total and state which digit changed (the tens) and which stayed the same (the ones).
  3. 3

    Ten more versus one more

    Why it works: Changing the ones digit (±1) and changing the tens digit (±10) are distinct moves; the child must adjust the correct digit for the correct operation.

    1. For the same starting number (for example 56), find 1 more and then 10 more; then find 1 less and 10 less.
    2. Say which digit changes each time: 1 more changes the ones (56 → 57); 10 more changes the tens (56 → 66).
    3. Explain in your own words how '10 more' is different from '1 more.'

Topic // Standards

Curriculum standards

Codes for the curriculum statements this topic maps to. Each publisher owns its standard text.
Common Core State Standards for Mathematics
1.NBT.5

Math // Number Representation & Place Value

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