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.

Share activities with pupils
Share function coming soon...

Lesson details

Key learning points

  1. When you add and subtract multiples of 10, the ones digit stays the same.
  2. When you add and subtract multiples of 10, the tens digit and sometimes the 100s digit will change.
  3. Number facts can help when adding and subtracting multiples of 10

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)

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.

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).

Video

Loading...

6 Questions

Q1.
Which number pairs have a total of 10?
Correct answer: 7 + 3
Correct answer: 2 + 8
5 + 4
0 + 9
Q2.
What is 40 + 10?
Correct Answer: 50, fifty
Q3.
What is 20 + 20?
Correct Answer: 40, forty
Q4.
What is 10 less than 103?
83
Correct answer: 93
97
113
Q5.
Match up the equations to the answers.
Correct Answer:125 − 10 =,115

115

Correct Answer:115 + 10 =,125

125

Correct Answer:115 − 10 = ,105

105

Correct Answer:125 + 10 = ,135

135

Q6.
Ping has a mass of 94 kg. Polly is 10 kg heavier. What is Polly's mass in kg?
An image in a quiz
Correct Answer: 104, one hundred and four

6 Questions

Q1.
Which numbers are multiples of 10?
65
Correct answer: 60
106
Correct answer: 140
Q2.
Which calculations cross the 100s boundary?
87 + 10
Correct answer: 101 − 10
Correct answer: 89 + 20
112 − 10
Q3.
What is 90 + 20?
Correct Answer: 110, one hundred and ten
Q4.
What is 116 − 10?
96
Correct answer: 106
115
126
Q5.
Penny is 95 cm tall. She puts on a green hat which is 30 cm tall. What is total height of Penny and her hat?
An image in a quiz
65 cm
105 cm
115 cm
Correct answer: 125 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?
An image in a quiz
Correct Answer: 67, 67 cm, sixty-seven