Module 4 Calculating
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Can I add or subtract a one-digit number to or from a two-digit number (bridging through a multiple of ten)?

Example review questions

  • What is 17 + 3? 17 + 4? 17 + 5? How did you work these out?
    A 28 + 5 bead string
  • What is the total of 28 and 5? Do you need to count on in ones? How can you partition 5 to help?
  • How can you work out 27 + 6? Can you work it out using two steps? Show me your steps on a number line.
  • What is 23 − 3? 23 − 4? 23 − 5? How did you work each of these out?
    A 42 bead string
  • What is 42 subtract 5? Do you need to count back in ones? How can you partition 5 to help?
  • How can you work out 24 − 6 using two steps? Show me your steps on a number line.

Teaching guidance

This teaching guidance document suggests some of the key vocabulary, models, images and practical equipment that children should experience and be able to use. It also includes some teaching tips to provide a few starting points for ways of supporting children with this area of mathematics.

PDF file Can I add or subtract a one-digit number to or from a two-digit number (bridging through a multiple of ten)? - teaching guidance | 51KB new window

Consolidation and practice

These resources are to support children in guided or independent work.

PDF file ITP Guide | 4317KB new window

SWF file Number Line ITP | 47KB new window

PDF file Year 2 Block A lesson notes | 1181KB new window
(pages 8 and 9)

Opportunities to use and apply

Possible contexts include:

  • Problems involving money and measures, e.g.
    5cm is cut off the following lengths of ribbon: 37cm, 34cm, 31cm, 39cm, 36cm, 32cm, 38cm. Which will be shorter then 30cm?
    Sam's best long jump so far was 75cm. Today he jumped 8cm further. How far did he jump? His friend has really long legs and jumped 8cm further than Sam jumped today. How far was that?
  • Problems involving time, e.g. It is 15 March today. What will the date be in one week's time?
  • Number sequences, e.g.
    A number line showing 8, 16, ?, ?, 40, 48

Confirming learning

Ask probing questions such as:

  • Sanjay drew two jumps on a number line to help him work out 48 + 7. What size jumps do you think he used? Why?
  • Rosie worked out 45 − 7 and got an answer of 42. Is she right? What do you think she did? Can the answer be more than 40? Why?
  • Jamie added a number to 37 and got the answer 44. How much did he add on? How might he have done it?
  • Explain how you would partition 5 when adding it to these numbers: 26, 27, 28 and 29. Explain how you would partition 6 when subtracting it from these numbers: 21, 22, 23 and 24.
  • Sam was trying to solve 47 + empty box = 52. He drew these jumps on a number line. What do you think the two jumps were and why?
    A number line showing 47, ?, 52