Starter quiz
- Izzy has 38 beads on her bracelet and she adds 55 more. Izzy now has ______ beads on her bracelet. Use the strategy you find most efficient to solve the problem.
- '93' ✓
- Which strategy is the most efficient when solving this problem? Izzy sees 62 ants and Andeep sees 21 ants. How many ants do they see altogether?
- Partition one addend
- Partition both addends
- Either of the above strategies ✓
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- Which of the following is the most efficient to solve this problem. Andeep’s string is 37 cm long and Izzy’s is 24 cm long. What will they measure when they put them together?
- Izzy sees 24 birds and Andeep sees 66 How many more birds does Andeep see? How many ones will be in the missing addend when the equation is written for this problem?
- 3 ones
- 4 ones
- 5 ones
- 2 ones ✓
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- There are 34 red sweets and 51 green sweets. How many more green sweets are there? What is the tens digit in the missing addend?
- 1 ✓
- 2
- 3
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- Izzy’s ladybird crawled 34 cm and Andeep’s ladybird crawled 67 cm. Andeep's ladybird crawled ______ cm further than Izzy's.
- '33' ✓
Exit quiz
- Izzy wants to solve the equation 38 − 2 = ? Which is the most efficient strategy to use?
- Use a known fact ✓
- Bridge 10
- Count back on your fingers
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Andeep has £65 and he buys a penguin. Which known fact should he use to calculate how much money he has left?- 65 − 4 = ?
- 60 − 40 =?
- 6 − 4 = ? ✓
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- Match each equation to say which digit will change when it is solved.
- 78 − 6 = ?⇔The ones digit will change from 8 to 2 ✓
- 87 − 60 = ?⇔The tens digit will change from 8 to 2 ✓
- Match the equations which will leave the same part remaining.
- 86 − 2 − 30 = ?⇔86 − 30 − 2 = ? ✓
- 86 − 20 − 3 = ?⇔86 − 3 − 20 = ? ✓
- 86 − 30 − 5 = ?⇔86 − 5 − 30 = ? ✓
Fill in the missing number to solve the equation. 65 − 34 = ?- '4' ✓
Which equation represents the number line?- 96 - 5 - 40 = 51 ✓
- 96 - 91 = 51
- 96 - 45 = 51 ✓
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- Known strategies can be used to help subtract two 2-digit numbers efficiently.
- It is important to be able to calculate mentally when beginning to subtract two 2-digit numbers.
Common misconception
Children do not always make the link to prior learning automatically, so when new numbers are introduced, they can sometimes revert to inefficient strategies.
It is important that the use of efficient strategies that are already known are focused upon when equations with new numbers are introduced so that prior knowledge can be used to support new learning and children can continue to work efficiently.
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.
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