New
New
Year 3

Choose the most efficient strategy to subtract from a 3-digit number

I can choose the most efficient strategy to subtract from a 3-digit number.

New
New
Year 3

Choose the most efficient strategy to subtract from a 3-digit number

I can choose the most efficient strategy to subtract from a 3-digit number.

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Lesson details

Key learning points

  1. By looking carefully at the minuend and subtrahend, we can choose the most efficient subtraction strategy.
  2. When numbers are close together, finding the difference is the most efficient strategy.
  3. Sometimes, we can use known addition facts to make finding the difference even more efficient.

Common misconception

Children will often reverse the minuend and subtrahend because they don't always appear in the order that they would in an expression.

Ensure that the children spend time understanding the context, either through discussion of the problem or through visual representations such as bar models. It's also worth spending time on vocabulary by playing fun word games or charades.

Keywords

  • Minuend - The minuend is the number being subtracted from.

  • Subtrahend - A subtrahend is a number subtracted from another.

  • Difference - The difference is the result after subtracting one number from another.

  • Partition - Partition is the act of splitting an object or value down into smaller parts.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Video

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6 Questions

Q1.
What is the missing whole in this bar model?
An image in a quiz
Correct Answer: 100
Q2.
Complete the missing word minuend − subtrahend = __________
Correct answer: difference
addend
minuend
sum
Q3.
Use a find the difference strategy to calculate: 72 − 65 =
Correct Answer: 7, seven, 7 ones, seven ons
Q4.
What is the difference between the two values shown?
An image in a quiz
Correct Answer: 70, seventy, seven tens, 7 tens
Q5.
Use a partitioning strategy to calculate 690 − 270 =
Correct Answer: 420, four hundred and twenty
Q6.
Which of the pairs of numbers have the smallest difference?
Correct answer: 270 and 290
230 and 310
260 and 320
250 and 280

6 Questions

Q1.
What is the equation being shown here?
An image in a quiz
Correct answer: 60 = 780 − 720
60 = 780 + 720
60 + 780 = 720
780 − 720
Q2.
Which strategy is being shown in this number line? Partitioning or counting on / back to find difference
An image in a quiz
Partitioning
Counting on to find the difference
Correct answer: Counting back to find the difference
Q3.
Use an efficient strategy to calculate the missing part in the bar model.
An image in a quiz
Correct Answer: 16, sixteen
Q4.
Use an efficient strategy to solve this problem: There are 330 children in the school. 270 of the children go on a school trip to the zoo. How many children do not go on the trip? children
Correct Answer: 60, 60 children, sixty children, sixty
Q5.
Use an efficient strategy to solve this problem: Lucas has read 168 pages of his book. Alex has read 57 pages. How many more pages has Lucas read? pages
Correct Answer: 111, 111 pages, one hundred and eleven pages, one hundred and eleven
Q6.
Use an efficient strategy to solve this problem: Alex and Jacob each collect football cards. Alex has 135 and Jacob has 82 cards. How many more cards does Alex have? cards
Correct Answer: 53, 53 cards, fifty three cards, fifty three