New
New
Year 2

Use number facts to add or subtract a one-digit number and a two-digit number.

I can add and subtract a single digit number and a two-digit number.

New
New
Year 2

Use number facts to add or subtract a one-digit number and a two-digit number.

I can add and subtract a single digit number and a two-digit number.

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Lesson details

Key learning points

  1. Known facts can be used to help solve equations with larger numbers.
  2. Partitioning a two-digit number into tens and ones can help with seeing the pattern in the ones.
  3. When adding to or subtracting from the ones without crossing the tens boundary, the tens digit does not change.

Keywords

  • Equation - An equation has an equal sign. It shows that what is on the left of the equation is equal to what is on the right.

Common misconception

Children may not recognise known facts when addends are presented in different order, e.g. they may not use 7+1 to solve 61 +7 They may also confuse tens and ones digits.

Focus on efficient ways of working and, when working in the abstract, partition the two-digit number into tens and ones, so the tens and ones digits can be easily identified and the commutative aspect of the ones digit can be more easily seen.

Do not include additions which sum to a multiple of ten or subtractions from a multiple of ten as these will be covered separately. When giving problems, also give the solution rather than asking children to solve, so that they maintain focus on the structure of the problem.
Teacher tip

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).

Lesson video

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6 Questions

Q1.
Which decade is missing on the number line?
An image in a quiz
the fifties
the sixties
Correct answer: the forties
Q2.
Alex subtracts 1 from these Base 10 blocks. Which image shows the number he now has?
An image in a quiz
An image in a quiz
An image in a quiz
Correct Answer: An image in a quiz
An image in a quiz
Q3.
Alex taps one more than the number shown. What number does he tap?
An image in a quiz
Correct Answer: 70, seventy
Q4.
Which number is missing?
An image in a quiz
Correct Answer: 90, ninety
Q5.
Which of the following could be Sam’s number?
An image in a quiz
Correct answer: 40
38
Correct answer: 70
Q6.
Alex thinks of a two-digit number. It is 1 less than a multiple of ten. It is greater than 80 but less than 90 What is his number?
Correct Answer: 89, eighty-nine, eighty nine

6 Questions

Q1.
Which equation would come next in the pattern?
An image in a quiz
2 + 7 = 9
12 + 7 = 19
22 + 7 = 29
Correct answer: 32 + 7 = 39
42 + 7 = 49
Q2.
Which known fact could be used to solve the equation shown on the number line?
An image in a quiz
Correct answer: 4 + 3 = 7
4 - 1 = 3
Correct answer: 3 + 4 = 7
5 + 5 = 10
Q3.
Which of the following equations can be solved using the known fact 3 + 5 = 8?
Correct answer: 45 + 3 =
58 + 3 =
Correct answer: 63 + 5 =
Q4.
Which number will make both of the following equations correct?
An image in a quiz
Correct Answer: 5, five
Q5.
Match the missing number equations to the correct answer.
Correct Answer:49 = ___ + 46,3

3

Correct Answer:___ + 6 = 49,43

43

Correct Answer:49 − ___ = 43,6

6

Q6.
What number did Alex add?
An image in a quiz
Correct Answer: 4, 4 ones