Why does my child answer 24 for 43 minus 27?

She is taking the smaller digit from the larger in each column, which feels like a sensible rule and gives a wrong answer every time the top digit is smaller. This is a place-value problem rather than a subtraction one. Build 43 with bundles of ten and loose ones, try to take seven ones from three, and let her discover that she must open a bundle. After doing that with her hands a few times, the written step has something to mean.

Should I teach borrowing or counting up?

Teach both and let the numbers decide which is used. Counting up is faster and far less error-prone when the two numbers are close together, as in 62 minus 58, and it is how adults make change at a checkout. The standard borrowing method is more efficient when the numbers are far apart and is needed for larger work later. A child who owns only one method will certainly use it in the wrong place.

My child can add but not subtract. Is that normal?

Very. Addition can be done by counting forward, which children already do well, while subtraction asks either for backward counting or for the inverse relationship, and both are harder. The gap usually closes when subtraction is taught as the missing part of an addition she already knows, rather than as a separate set of facts to be memorized from the beginning.

When should we use a number line?

Whenever the answer is being hunted rather than known, and then less and less. A number line makes counting back and counting up both visible, and makes the difference between them obvious at a glance. Retire it in stages: a line on the floor, then a paper line, then a line she draws herself with only the two numbers marked, then nothing. Keeping it forever slows recall; removing it too early produces guessing.

How to Teach Subtraction — Readiness, Practice, Mastery

Subtraction answers three different questions with one symbol: how many are left, how many more one group has than another, and what the missing part is. Children who only ever meet the first one struggle with word problems later. Teach all three with objects, teach counting up as well as counting back, and keep the matching addition fact in view.

The three questions subtraction answers

Take-away is the familiar one: twelve crackers, you eat five, how many are left. Comparison sounds nothing like it, since you have twelve and your sister has five and the question is how many more you have, with nothing removed at all. Missing part is the third: twelve altogether, five on the table, how many under the cup. Word problems from second grade onward draw on all three, so all three need practicing by name.

Counting back suits small amounts taken away, since fifteen minus two is an easy walk backward. Counting up suits close numbers, because fifteen minus thirteen is two steps forward and a long, error-prone journey the other way. A child should be choosing between the two by looking at the numbers first, and that choice is worth saying out loud every time.

Ten minutes a day, and what to say

The session mirrors your addition routine, and that is deliberate: the two operations should feel like one family rather than two subjects. Keep the objects out longer than feels necessary. The moment subtraction moves to paper only, the three problem types quietly collapse back into take-away and the child stops asking herself what is actually being requested.

Three minutes, the hidden-part game: count ten counters, she shuts her eyes, you cover some, she says how many are hidden.
Two minutes, oral fact families: "Seven and five is twelve, so twelve take away five is what?"
Two minutes, one word problem of each type, said aloud and acted out with the counters.
Two minutes, counting up: "Start at 38 and get to 45. How many steps?"
One minute written: four problems, one of them with the answer blank in the middle.

Coins, a cup, and a line on the floor

A pretend store with real coins is the best subtraction material in the house, because making change is counting up in disguise: the item cost 34 cents, you gave 50, so count from 34 up to 50. A paper number line taped along the floor lets a child walk the distance in both directions with her feet, which is what makes counting back and counting up feel like two different journeys rather than two rules. An opaque cup set over some of the counters creates a missing part you can ask about.

How to tell it has landed

It is working when she chooses the method to fit the numbers, when she can restate a subtraction as an addition with a part missing, and when she notices that an answer larger than the number she started with has to be wrong. That last self-check is worth more than speed, and it is the one that survives into larger numbers.

She counts backward for everything, so 15 - 13 takes as long as 15 - 2.
She gives 24 for 43 - 27, taking the smaller digit from the larger in each column.
She reads a comparison problem and adds the two numbers.
She cannot state the addition fact that matches the subtraction she has just done.
She borrows on every problem, including the ones that do not need it.

Backing up when it falls apart

Go back to totals of ten with the cup game until the missing part comes without counting, because that is the idea the whole operation rests on. Then bring back fact families with objects, saying all four sentences aloud for the same three numbers. For an error like 43 minus 27 giving 24, the answer is not a reminder about borrowing but bundled materials: build 43, try to remove seven ones, find that you cannot, and open a bundle of ten in front of her.

A realistic timeline

Subtraction within ten usually settles in kindergarten or early first grade, within twenty across first grade, and two-digit subtraction with regrouping across second grade, often with a stall somewhere in the middle of it. Three-digit subtraction across zeros is a third-grade struggle for most children and is entirely normal to teach more than once. Place value, not more fact drill, is what finally makes it come right.

First, your child should already…

This skill builds directly on:

Addition — master this first.

What your child is learning

Subtraction is the inverse of addition. Children need to see it as taking away, comparing, and finding missing parts, not only as a memorized procedure.

Signs your child is ready

Understands part-whole models
Can count backward or count up
Recognizes related addition facts

The common stumbling point

Treating subtraction as a direction to always count backward, even when counting up or using a related addition fact would be clearer.

Practice this skill

Worksheets and decodable practice for Subtraction are in the library.

Kindergarten — Subtraction as Separating 166 worksheets
Grade 1 — Subtraction with Regrouping 20 worksheets
Grade 2 — Subtraction with Regrouping 20 worksheets
Grade 3 — Subtraction with Regrouping 20 worksheets
Grade 4 — Subtraction with Regrouping 20 worksheets
Grade 5 — Subtraction with Regrouping 20 worksheets

Every set opens its first three worksheets to everyone; the rest are included with All Access.

Browse the whole practice library

How to know it’s mastered

The child solves grade-level subtraction and explains whether the problem is take-away, compare, or missing part.

Common questions

Why does my child answer 24 for 43 minus 27?: She is taking the smaller digit from the larger in each column, which feels like a sensible rule and gives a wrong answer every time the top digit is smaller. This is a place-value problem rather than a subtraction one. Build 43 with bundles of ten and loose ones, try to take seven ones from three, and let her discover that she must open a bundle. After doing that with her hands a few times, the written step has something to mean.
Should I teach borrowing or counting up?: Teach both and let the numbers decide which is used. Counting up is faster and far less error-prone when the two numbers are close together, as in 62 minus 58, and it is how adults make change at a checkout. The standard borrowing method is more efficient when the numbers are far apart and is needed for larger work later. A child who owns only one method will certainly use it in the wrong place.
My child can add but not subtract. Is that normal?: Very. Addition can be done by counting forward, which children already do well, while subtraction asks either for backward counting or for the inverse relationship, and both are harder. The gap usually closes when subtraction is taught as the missing part of an addition she already knows, rather than as a separate set of facts to be memorized from the beginning.
When should we use a number line?: Whenever the answer is being hunted rather than known, and then less and less. A number line makes counting back and counting up both visible, and makes the difference between them obvious at a glance. Retire it in stages: a line on the floor, then a paper line, then a line she draws herself with only the two numbers marked, then nothing. Keeping it forever slows recall; removing it too early produces guessing.

What comes next

Once this is solid, move on to:

Place Value →