New
New
Year 3
Cross the hundreds boundary when adding and subtracting any 2-digit multiple of 10
I can cross the 100s boundary when adding and subtracting multiples of ten.
New
New
Year 3
Cross the hundreds boundary when adding and subtracting any 2-digit multiple of 10
I can cross the 100s boundary when adding and subtracting multiples of ten.
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Lesson details
Key learning points
- When you add and subtract multiples of 10, the ones digit stays the same.
- When you add and subtract multiples of 10, the tens digit and sometimes the 100s digit will change.
- Number facts can help when adding and subtracting multiples of 10
Keywords
Multiple - The result of multiplying a number by another whole number.
100s boundary - The point at which the numbers change into 100s numbers, or from one set of hundreds to another.
Common misconception
Pupils may have difficultly partitioning 10s when crossing the 100s boundary. (e.g. 125 - 40)
Pupils practice adding to/subtracting from multiples of 10 (e.g. 130 - 50) before exploring non-multiples of 10 (e.g. 85 + 30)
Many pupils will find base ten blocks an essential resource for this lesson. Pupils should also be encouraged to use number lines to represent the problems, as they support children's thinking when crossing the hundreds boundary.
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).
Starter quiz
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6 Questions
Q1.
Which number pairs have a total of 10?
5 + 4
0 + 9
Q2.
What is 40 + 10?
Q3.
What is 20 + 20?
Q4.
What is 10 less than 103?
83
97
113
Q5.
Match up the equations to the answers.
115
125
105
135
Q6.
Ping has a mass of 94 kg. Polly is 10 kg heavier. What is Polly's mass in kg?
Exit quiz
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6 Questions
Q1.
Which numbers are multiples of 10?
65
106
Q2.
Which calculations cross the 100s boundary?
87 + 10
112 − 10
Q3.
What is 90 + 20?
Q4.
What is 116 − 10?
96
115
126
Q5.
Penny is 95 cm tall. She puts on a green hat which is 30 cm tall. What is the total height of Penny and her hat?
65 cm
105 cm
115 cm
Q6.
Piper and her blue hat have a total height of 107 cm. If her hat is 40 cm tall, how tall is Piper in cm?