Addition number family foundations continued

The process

Students learn two rules to follow to figure out the missing number in an addition number family.

• If the big number is missing, you add to find the missing number.
• If a small number is missing, you subtract to find the missing number.

Starting in lesson four, students continue oral work with number families and written work is added.

The process is:

• Say, ‘These are the same families we just worked with. Touch family A’, and scan. ‘What’s missing – the big number or a small number?’ and signal. ‘Say the problem you work to find the missing number’, and signal.
• Say, ‘Write the problem for family A next to the number family. Remember to write the problem so that tens digits and ones digits are lined up. Don’t work the problem, just write it.’ Observe students and give feedback.
• Say, ‘Check your work’, and display. ‘Here’s what you should have.’
• Continue the process with the other problems.