New
New
Year 2

Combine tens and ones within equations

I can combine and partition tens and ones in the context of equations.

New
New
Year 2

Combine tens and ones within equations

I can combine and partition tens and ones in the context of equations.

Lesson details

Key learning points

  1. Known strategies can be used to help us prepare for the addition of two 2-digit numbers.
  2. It is important to be able to calculate mentally before adding two 2-digit numbers.

Common misconception

Children may rely on the order of the addends rather than their place value when calculating. They may also default to counting on rather than using known facts.

Refer back to known facts and efficient strategies and model their use throughout, discussing the best strategy to use at each point and why. Model errors that can be made when not adding ones then tens for example, or in counting on in ones.

Keywords

  • Calculate - To work out an answer, often by adding or subtracting.

  • Efficiently - Not wasting time or effort. An efficient strategy is one we can carry out easily.

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).

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6 Questions

Q1.
Andeep wants to solve the equation 2 + 40 + 50 = ? Which is the most efficient strategy to use?
Correct answer: use a known fact
bridge 10
think of a Gattegno chart
Q2.
Andeep estimates the cost of the items shown. Which of the following is most likely to be accurate?
An image in a quiz
The sum will be in the twenties.
Correct answer: The sum will be in the thirties
The sum will be in the forties.
Q3.
For which of the following equations would you use the bridge 10 strategy?
34 + 20 = ?
34 + 2 = ?
Correct answer: 34 + 7 = ?
Q4.
For which equations would you use the known facts strategy? Tick two.
Correct answer: 64 + 30 = ?
Correct answer: 64 + 3 = ?
64 + 8 = ?
Q5.
Andeep’s items cost £54 Which of the following will be the cost of Izzy’s items?
An image in a quiz
£55
£56
Correct answer: £53
Q6.
Match to show which equations will have the same sum.
Correct Answer:36 + 7 = ,37 + 6 =

37 + 6 =

Correct Answer:32 + 9 = ,39 + 2 =

39 + 2 =

Correct Answer:35 + 3 = ,33 + 5 =

33 + 5 =

6 Questions

Q1.
Use the Base 10 blocks shown to solve the equation.
An image in a quiz
Correct Answer: 69
Q2.
Match the expressions which have the same value.
Correct Answer:40 + 1 + 3 + 20,1 + 40 + 3 + 20

1 + 40 + 3 + 20

Correct Answer:30 + 1 + 20 + 4,4 + 1 + 30 + 20

4 + 1 + 30 + 20

Correct Answer:10 + 2 + 30 + 4,2 + 10 + 30 + 4

2 + 10 + 30 + 4

Q3.
What is the missing whole in the bar model?
An image in a quiz
98
Correct answer: 89
69
Q4.
Tick the correct equation.
4 + 50 + 2 + 20 = 67
20 + 4 + 2 + 50 = 67
Correct answer: 5 + 20 + 40 + 2 = 67
Q5.
Match the equations to the correct missing addend.
Correct Answer:7 + 1 + ___ + 20 = 68,40

40

Correct Answer:30 + 2 + ___ + 5 = 57 ,20

20

Correct Answer:20 + 40 + ___ + 2 = 65,3

3

Q6.
Which of the digit cards shown would complete the equation?
An image in a quiz
Correct answer: 2 and 3
3 and 4
4 and 5