New
New
Year 2

Use efficient addition strategies to calculate

I can identify addition strategies to calculate efficiently.

New
New
Year 2

Use efficient addition strategies to calculate

I can identify addition strategies to calculate efficiently.

Lesson details

Key learning points

  1. We can use strategies we already know 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 not be able to mentally calculate or identify efficient strategies and so revert to counting on in ones.

Assess use of mental strategies before starting this lesson as it is important to be fluent in using strategies with smaller numbers before working with larger numbers to avoid reverting to inefficient counting strategies.

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.

It is important that children calculate mentally and explain each strategy used throughout, moving quickly between questions and contexts to ensure fluency.
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).

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6 Questions

Q1.
Look at the items in the shop. How much would a ball and a car cost? £
An image in a quiz
Correct Answer: 7, £7
Q2.
Izzy buys an astronaut and a rocket. Which known fact would she use to help her calculate the cost?
An image in a quiz
3 + 4
Correct answer: 4 + 5
3 + 5
Q3.
Andeep spent £43 at the shop. Which two items did he buy?
An image in a quiz
Correct answer: the ball and the astronaut
the rocket and the ball
the astronaut and the car
Q4.
Which known fact would you use to calculate the cost of a penguin and an astronaut?
An image in a quiz
4 + 2 = 6
Correct answer: 4 + 4 = 8
42 + 4
Q5.
Which known fact would you use to calculate the cost of a unicorn and a car?
An image in a quiz
Correct answer: 4 + 4 = 8
6 + 4 = 10
64 + 4 = 68
Q6.
Andeep uses the 'bridge 10' strategy to find the cost of two items. Which two items were they?
An image in a quiz
the gloves and the trainers
the socks and the t-shirt
Correct answer: the sunglasses and the trainers

6 Questions

Q1.
Izzy wants to solve the equation 2 + 4 + 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
Correct answer: The cost will be in the forties.
The cost will be in the fifties.
The cost will be in the sixties.
Q3.
For which of the following equation, would you use the bridge 10 strategy?
45 + 3 = ?
45 + 4 = ?
Correct answer: 45 + 8 = ?
Q4.
For which equations would you use the known facts strategy? Tick two.
42 + 9 = ?
Correct answer: 42 + 30 = ?
Correct answer: 42 + 3 = ?
Q5.
Andeep’s items cost £35 Which of the following shows the cost of Izzy’s items?
An image in a quiz
£34
Correct answer: £36
£35
Q6.
Match to show which equations will have the same sum.
Correct Answer:44 + 6 = ,46 + 4 =

46 + 4 =

Correct Answer:47 + 5 = ,45 + 7 =

45 + 7 =

Correct Answer:42 + 3 = ,43 + 2 =

43 + 2 =