lesson
Parts make a whole
Read with an adult. You can say, point, draw or write your answer.
1 · Learn
A number bond shows parts that make a whole. If 7 and 3 make 10, then 17 and 3 make 20.
Keep the whole the same while you change the parts. If one part gets one bigger, the other must get one smaller.
A fact about ones can help with tens. Three ones and seven ones make ten ones. Three tens and seven tens make ten tens: 30 + 70 = 100. Taking away seven tens leaves three tens: 100 − 70 = 30.
2 · Worked example
I know 6 + 4 = 10. Adding ten to the first part gives 16 + 4 = 20. Changing every one to a ten gives 60 + 40 = 100. These are two different changes.
3 · Your turn
Fill the gaps: 8 + __ = 10; 18 + __ = 20; 20 − 6 = __. Now use 8 + 2 = 10 to find 80 + 20 and 100 − 20.
Check your answer
2; 2; 14. Eight tens and two tens make ten tens, so 80 + 20 = 100. Removing two tens leaves eight tens: 100 − 20 = 80.
4 · Apply your learning
Use twenty counters to make pairs of parts. Then use ten bundles, each containing ten sticks, to model a related fact with a whole of 100. Say whether each piece represents one or ten.
Adult guidance and safety
Use practical objects before symbols. Read the task aloud when needed and ask the child to explain, not just name an answer. Revisit with different examples; one successful answer is not proof of fluency.
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