Solving the Mystery of Unknowns
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Solving the Mystery of Unknowns
Year 7-8 Mathematics Understanding Open Number Sentences WALT: Identify and solve simple algebraic expressions
What is an Open Number Sentence?
A number sentence with a missing part Uses a blank space or box for the unknown Example: 2 + 5 = 3 + ___ The equal sign means 'the same as'
Detective Challenge: Find the Missing Number
Look at this number sentence: 7 = 3 + ___ Use counters or your fingers to help What number makes both sides equal? Discuss your answer with a partner
Solving Strategies
Use manipulatives (counters, blocks) Think: 'What makes both sides equal?' Check your answer by counting both sides The equal sign is like a balance scale
Practice Examples
{"left":"4 + 2 = ___ + 1\n8 = 5 + ___\n___ + 3 = 7\n6 + 1 = 4 + ___","right":"Answer: 5\nAnswer: 3\nAnswer: 4\nAnswer: 3"}
Create Your Own Mystery
Work in pairs Create 3 open number sentences Use numbers 1-10 Challenge your partner to solve them!
Quick Check: True or False?
5 + 3 = ___ + 4 Is this true if the blank equals 4? Show thumbs up for TRUE Show thumbs down for FALSE
Success! You've Solved the Mystery
We learned what open number sentences are We used the equal sign to mean 'the same as' We solved problems using different strategies Next lesson: More challenging unknowns!