Subtracting with the standard algorithm – Grade 4 math lesson
Lesson 9 of 26 in the Grade 4 math course
US version. US grades, US spelling and dollars ($). · UK Maths Department
A complete 45-minute lesson for grade 4 (ages 9–10) that runs on this page – at school or at home. Every answer is graded right away, with a worked explanation.
- Time
- 45 minutes + 20 min homework
- Grade
- Grade 4 (ages 9–10)
- You need
- Paper, a pencil and this page
- Graded
- Instantly, with explanations
For parents: how to use this lesson
You don't need to know this topic yourself. The lesson explains each step on screen, one tidy step at a time. Every answer is graded straight away with a worked explanation, so you never have to grade anything.
- Read what your child will learn and the big ideas together.
- Press Start the lesson below and sit with your child for the teaching and the worked examples (about 19 minutes).
- Let them do the practice on their own. They choose Getting started, On track or Challenge – start on On track and move up after a few right in a row.
- Finish with the exit ticket and the talk question: “Explain what happens when you need to regroup from a zero.”
- Later that day or the next day: the homework (20 minutes), then a practice test.
Watch out for
- Taking the smaller digit from the bigger one whatever the order (e.g. 2 − 7 written as 5). Read each column aloud as "top take away bottom"; if you cannot, regroup.
- Forgetting to reduce the column you regrouped from. Always cross out and rewrite the digit as soon as you regroup.
- Getting stuck at a zero. Show 400 − 1 with base-ten blocks: a hundred is regrouped for 10 tens, then a ten for 10 ones.
Tip for home: Work out change or the difference between two heights, then check by adding.
What your child will learn
Learning goal: subtract numbers using the standard algorithm for subtraction.
Success looks like
- I can line up the digits.
- I can regroup when the top digit is smaller.
- I can check my answer by adding.
Key words
- the standard algorithm for subtraction
- a written method that subtracts one column at a time
- regroup
- regroup 1 ten as 10 ones (or 1 hundred as 10 tens)
- difference
- the answer to a subtraction
- inverse
- the opposite operation: addition undoes subtraction
What to have ready
- Paper and a pencil
- This page on a computer, tablet or phone
- For the hands-on part: Use base-ten blocks to show a regroup: break a ten into ten ones, then write the same calculation in columns. No base-ten blocks? Draw tens as sticks and ones as dots, and cross out a stick to make ten dots.
The big ideas (for the adult)
In the standard algorithm for subtraction, write the larger number on top and line up the digits. Start with the ones.
If the top digit is smaller than the bottom digit, regroup: take one from the next column to the left and make the top digit ten more. Cross out and rewrite the digit you regrouped from.
When the next column is a zero, go further left: regroup through the zero, which then becomes 9. Check by adding your answer to the number you subtracted.
The lesson, step by step
| Part | Time | How it is checked |
|---|---|---|
| Starter: quick recall | 5 min | Graded by Classfern |
| Teaching input | 10 min | Not assessed, self-checked |
| Worked examples and guided practice | 9 min | Not assessed, graded by Classfern |
| Independent practice | 15 min | Graded by Classfern |
| Closure and exit ticket | 6 min | Graded by Classfern, self-checked |
Starter, "your turn", practice and exit ticket are graded by Classfern. Worked examples and teaching are not assessed. The hands-on task and the reflection are self-assessed. Explanations in talk are judged by the parent and not recorded.
The lesson
It runs here on the page. No sign-up and no names – progress is kept only in this browser.
Homework and practice at home
20 minutes: 10 practice questions, 3 multiple-choice questions and 2 to remember from earlier work, then a short reflection. New questions every time, all graded instantly.
More practice
More Grade 4 math lessons
- Factors and multiples
- Prime and composite numbers
- Multiplication and division
- Solving word problems
- Number patterns
- Place value: the value of each digit
- Rounding to the nearest 10, 100 or 1,000
- Adding with the standard algorithm
- Decimals: tenths, hundredths and thousandths
- Comparing, ordering and writing numbers
- Equivalent fractions
- Adding and subtracting fractions with like denominators
- Fractions of a whole number
- Comparing and simplifying fractions
- Fractions, decimals and percentages
- Area of rectangles
- Perimeter
- Finding unknown angles
- Converting units of time
- Line plots
- Converting measurement units
- Measuring angles
- Classifying 2-D shapes
- Lines of symmetry
Curriculum
Common Core State Standards 4.NBT.B.4: “Fluently add and subtract multi-digit whole numbers using the standard algorithm.”
Our lessons and questions are our own. They are not written or endorsed by any government department, testing agency or exam board.