Add two-digit numbers without crossing the tens boundary | Maths

Starter quiz

Use the Base 10 blocks shown to solve the equation

'87' ✓
Match the expressions which have the same value.

50 + 1 + 3 + 20

⇔

3 + 1 + 50 + 20 ✓

20 + 2 + 30 + 4

⇔

2 + 30 + 4 + 20 ✓

50 + 2 + 40 + 4

⇔

2 + 40 + 50 + 4 ✓
What is the missing whole in the bar model?

77

68

86 ✓
Tick the equation which is correct.

30 + 2 + 60 + 1 = 57

3 + 5 + 30 + 40 = 78 ✓

5 + 20 + 4 + 50 = 97
What is the missing addend in the equation? 5 + ___+ 40 + 20 = 67

'2' ✓
Which of the digit cards shown would complete the equation?

2 and 4

4 and 5 ✓

5 and 6

Exit quiz

Match the expressions which will have the same value.

34 + 23

⇔

4 + 3 + 30 + 20 ✓

23 + 32

⇔

30 + 2 + 20 + 3 ✓

43 + 32

⇔

3 + 30 + 40 + 2 ✓
Which expression will have the same sum as 45 + 23?

54 + 32

43 + 25 ✓

52 + 43
Which equation will have a sum in the nineties?

43 + 52 = ? ✓

23 + 46 = ?

42 + 27 = ?
Which equation will have a sum greater than 54 + 21 = ?

45 + 12 = ?

54 + 41 = ? ✓

51 + 24 = ?
52 + 34 = 50 + ______ + 30 + 4

'2' ✓
35 + 52 = 87, so 32 + 55 = ______

'87' ✓

Worksheet

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Presentation

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Lesson Details

Key learning points

Two-digit numbers can be added by using Base 10 equipment to combine the tens and the ones.
Partitioning two-digit numbers can help when adding them.
Either the tens or the ones can be added first, the sum will remain the same.
Considering the number of tens when adding two-digit numbers can help estimate the sum.

Common misconception

Children may transpose digits in the numbers, so add tens as ones and vice versa. They may also use inefficient counting strategies to count on in tens, then ones.

Ensure that the numbers are partitioned into tens and ones, so their place value is clear and the link to known facts can be easily seen. Refer back to known facts using the stem sentence 'I know that..., so I know that ...'

Keywords

Partition - To split a whole up into parts.