10.3 Small Group · Group 2
Second Challenge Form · Non-Routine Extension · Same Standard, New Problems
puzzle · pattern · Procedural Fluency · Reasoning & Critique
- You already can do this. So we go up a level, not up a number: find what is always true, show it a second way, and be ready to defend it with a reason instead of an answer.
- Before moving anything, I describe what the solved puzzle will look like: the discs in the same order — smallest on top to largest on bottom — but on a different rod.
- Then I play the small cases: a one-disc tower takes 1 move, and a two-disc tower takes 3 moves.
- A three-disc tower takes at least 7 moves. Small cases are how mathematicians play.
- Discs: 1, 2, 3 — Steps: 1, 3, 7. What is happening from each row to the next?
- Double the number of steps and add 1: 1 doubled plus 1 is 3, and 3 doubled plus 1 is 7.
- So 4 discs take 7 × 2 + 1 = 15 steps, and 5 discs take 15 × 2 + 1 = 31 steps.
- The pattern just solved a puzzle we never touched.
- Now prove it: say why that move had to work at all — not just that it did.
- Sentence frame — convince a skeptic: "My method works because ___ . It would stop working if ___ ."
- puzzle (rompecabezas) — A problem designed to be played with — it has rules, a goal, and room to imagine solutions.
- pattern (patrón) — Something that repeats or changes in a predictable way.
- pattern rule (regla del patrón) — A rule that tells you how to get the next value in a pattern from the one before it.
- predict (predecir) — To say what will happen before it happens, using a pattern or reasoning.
- organize (organizar) — To arrange information — often in a table — so patterns become easier to see.
- Doubling the previous number of steps but forgetting to add 1 — answering 14 instead of 15 for four discs, or 30 instead of 31 for five.
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1 MULTIPLE CHOICE
Look at the table a different way: 1 disc → 1, 2 discs → 3, 3 discs → 7, 4 discs → 15, 5 discs → 31. Which describes the relationship between the number of discs and the number of steps?
- AThe steps are 1 less than a doubling pattern: 2, 4, 8, 16, 32 each minus 1
- BThe steps are the number of discs multiplied by itself
- CThe steps are 6 times the number of discs, plus or minus 1
- DThe steps are the two previous step counts added together
✏️ Workspace & Solution Steps -
2 MULTIPLE CHOICE
The table shows 1 disc → 1 step, 2 discs → 3 steps, 3 discs → 7 steps. What is the pattern rule for the number of steps when you add one more disc?
- ADouble the number of steps and add 1
- BAdd 2 to the number of steps
- CAdd the number of discs to the steps
- DMultiply the number of steps by 3
✏️ Workspace & Solution Steps -
3 MULTIPLE CHOICE
Use the pattern rule to complete the table: how many steps for a four-disc tower?
- A15 steps
- B14 steps
- C9 steps
- D28 steps
✏️ Workspace & Solution Steps -
4 MULTIPLE CHOICE
What is the minimum number of steps to solve a FIVE-disc Tower of Hanoi puzzle?
- A31 steps
- B15 steps
- C30 steps
- D35 steps
✏️ Workspace & Solution Steps
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5 OPEN RESPONSE
The 15 Puzzle is a sliding puzzle with 15 tiles in a frame 4 tiles high by 4 tiles wide. You arrange the tiles from 1 to 15 by sliding one tile at a time into the open space. Sometimes it is solvable and sometimes it is not. How would you make an argument about whether a particular 15 Puzzle is solvable, using what this lesson taught about being playful?
✏️ Mathematical Justification & Response -
6 ERROR ANALYSIS
Fix our table's thinking
- 1The problem:Why is finding a pattern MORE powerful than just solving the three-disc puzzle by hand?
- 2A classmate at our table answered:The pattern lets you skip the rules of the puzzle
Which step contains the error? Explain the mathematical misconception and write the correct calculation below.
✏️ Corrected Mathematical Work & Explanation
Writing Task: Justify why your mathematical solution is accurate and complete.