New
New
Year 3

Choose the most efficient strategy to add two 3-digit numbers

I can choose the most efficient strategy to add two 3-digit numbers.

New
New
Year 3

Choose the most efficient strategy to add two 3-digit numbers

I can choose the most efficient strategy to add two 3-digit numbers.

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Lesson details

Key learning points

  1. By looking carefully at the addends, we can choose the most efficient addition strategy.
  2. Sometimes an adjusting strategy is the most efficient.
  3. Sometimes a redistributing strategy is the most efficient.
  4. Sometimes a partitioning and bridging strategy is the most efficient.

Common misconception

Pupils will often know one method, such as partitioning, and stick to it without trying any others. Sometimes, some pupils will be very reluctant to move away from written methods such as columns.

Reinforce the idea of bravery and courage to try new methods. Remind them that efficiency is partly about speed and they might find that other methods only become quick with practice!

Keywords

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

  • Adjust - When you adjust you make a small change to a number. This can make a calculation easier to solve mentally.

  • Redistribute / redistribution - Redistribution is where part of one addend is moved to another addend.

  • Efficient - Working efficiently means finding a way to solve a problem quickly whilst also maintaining accuracy.

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 number pair to ten for 6?
Correct Answer: 4, four
Q2.
What is the number pair to 100 for 30?
Correct Answer: 70, seventy
Q3.
Each bundle contains ten straws. How many straws are there altogether?
An image in a quiz
Correct Answer: 120, one hundred and twenty
Q4.
Match the units to their value.
Correct Answer:3 tens,30

30

Correct Answer:6 tens,60

60

Correct Answer:4 ones,4

4

Correct Answer:10 tens,100

100

Q5.
Fill in the missing number in this sequence: 70, 80, 90, 100, , 120, 130, 140
Correct Answer: 110, one hundred and ten
Q6.
Fill in the missing number in this sequence: 170, 175, 180, 185, , 195, 200, 205
Correct Answer: 190, one hundred and ninety

6 Questions

Q1.
102 + 130 = 232 is calculated using partitioning, adjustment or redistribution and represented using base ten. Which of the three methods is shown?
An image in a quiz
Partitioning
Adjustment
Correct answer: Redistribution
Q2.
102 + 130 = 232 is calculated using partitioning, adjustment or redistribution and represented using base ten. Which of the three methods is shown?
An image in a quiz
Partitioning
Correct answer: Adjustment
Redistribution
Q3.
102 + 130 = 232 is calculated using partitioning, adjustment or redistribution and represented using base ten. Which of the three methods is shown?
An image in a quiz
Correct answer: Partitioning
Adjustment
Redistribution
Q4.
Which of these two words describes how a solution is found 'efficiently'?
Correct answer: quickly
excitedly
Correct answer: accurately
importantly
slowly
Q5.
Which method would best solving 507 + 260?
Correct answer: Partitioning
Adjustment
Redistribution
Q6.
Match the equations with the method which was most efficient for finding the sum.
Correct Answer:198 + 199,Adjustment

Adjustment

Correct Answer:345 + 201,Redistribution

Redistribution

Correct Answer:509 + 460,Partitioning

Partitioning