New
New
Year 2

Solve problems involving subtraction when bridging 10

I can solve problems involving subtraction of two-digit numbers that cross the tens boundary.

New
New
Year 2

Solve problems involving subtraction when bridging 10

I can solve problems involving subtraction of two-digit numbers that cross the tens boundary.

Lesson details

Key learning points

  1. Some problems involving the subtraction of two-digit numbers, can be solved by bridging 10
  2. We can look to see if the ones digits cross the tens boundary to find out if we must use the bridge 10 strategy

Common misconception

When subtracting, children may partition the whole and the part, look at the ones digits involved and simply subtract the smaller digit from the larger digit, e.g. solve 75 - 36 as 70 - 30, then 6 - 1

Consider whether or not the equation involved will require the 10 tens boundary to be crossed before solving, referring specifically to subtracting the ones digit from the whole number, e.g. think 75-6 rather than 5 -6

Keywords

  • Partition - To split a whole up into parts

  • Part - A piece or section of a whole

  • Bridge 10 - An addition or subtraction strategy where numbers are partitioned to reach the previous or next multiple of 10, so bonds to 10 can be used to calculate more efficiently.

Encourage children to 'think out loud' when solving problems and model this, representing problems visually so the structure is fully understood. Then, focus on the numbers involved and make decisions about the most efficient method to calculate.
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.
Which equation has a whole that is a multiple of 10?
Correct answer: {{ }} − 34 = 26
{{ }} − 46 = 55
{{ }} − 81 = 18
Q2.
Which bar model represents the equation shown? 61 = 93 − ?
Correct answer: A
B
C
Q3.
Write the addition equation you would use to check this subtraction. 84 − 37 = 47
Correct Answer: 37 + 47 = 84
Q4.
Which number would solve the equation. 54 − = 31
85
Correct answer: 23
32
Q5.
Which bar model would represents the equation shown? − 14 = 46
A
Correct answer: B
C
Q6.
Solve the equation − 27 = 29
Correct Answer: 56

6 Questions

Q1.
In which of the following equations will you have to bridge 10?
34 − 13 = ?
Correct answer: 56 − 27 = ?
83 − 42 = ?
Q2.
Which of the following equations is correct?
32 − 26 = 14
84 − 32 = 56
Correct answer: 93 − 64 = 29
Q3.
Solve the following equation. 75 − 47 =
Correct Answer: 28
Q4.
64 tickets are needed to buy a cap and the unicorn. If the unicorn costs 36 tickets, how much does the cap cost? tickets.
An image in a quiz
Correct Answer: 28
Q5.
Izzy had 85 tickets and she bought a pair of sunglasses at the ticket shop. Now, she has 38 tickets left. How much did the sunglasses cost? tickets.
An image in a quiz
Correct Answer: 47
Q6.
Match each equation to the correct answer.
Correct Answer:69 − 21 = ___,48

48

Correct Answer:71 − 39 = ___ ,32

32

Correct Answer:55 − ___ = 27,28

28