Four Unit Fractions Make One

Create the complete investigation-led core lesson for Section 7.9-B. Use Sana only. Do not invent the six solution sums: the supplied planning source states that the textbook puzzle has six solutions but does not list the exact sums. Build the lesson so verified textbook solutions can be inserted in post-production. 1. OPEN THE PUZZLE BOARD: show 1/□ + 1/□ + 1/□ + 1/□ = 1. Ask whether it is possible for all four to be different unit fractions. 2. RECALL: briefly connect to the previous discovery 1/2 + 1/3 + 1/6 = 1. Explain that in this puzzle each numerator is 1 and all four fractions must be distinct. 3. MODEL SYSTEMATIC REASONING: start with a plausible larger unit fraction, then use smaller unit fractions to fill the remaining amount. Explain that each choice changes the remainder available for the other fractions. 4. COMMON FRACTIONAL UNITS: demonstrate how to rewrite fractions using a common denominator to test whether a proposed sum is exactly 1. Use one clearly labelled illustrative trial only if the equality is verified. 5. SIX SOLUTION CARDS: prepare six separate cards for the six exact textbook solutions. Insert the verified sums from the complete textbook source before final animation. Animate each verified sum filling one whole circle or fraction strip. Do not fabricate or approximate any missing solution. 6. THINKING QUESTIONS: ask what changes when one unit fraction is replaced by a smaller one, and how the remaining fractions must compensate. Give learners time to reason before showing the verified cards. 7. FINAL CHALLENGE: “Can you find one solution without looking at the cards? Can you explain why it equals one?” Leave this as a learner task. 8. TRANSITION to an interactive “Egyptian Fraction Mystery” activity. Visual style: story-led puzzle lab with clean fraction circles/strips, large readable denominators and accurate equal partitions. Do not present unverified solution sums. If the complete textbook list is unavailable at production time, show six labelled placeholders or stop before revealing the answers and flag that the exact solution set needs source verification.