The Pancake Problem
⏱ 0:33📘 Grade 4 · Optimisation
A pan holds 2 pancakes and each side takes 3 minutes. Never leave a space empty and 3 pancakes take 3 rounds, 9 minutes, instead of 12.
The videos are narrated in Mandarin Chinese with on-screen subtitles.
📚 What you will learn
- 3 pancakes have 6 sides to cook; the pan cooks 2 sides per round, so at least 6 ÷ 2 = 3 rounds.
- Round 1: pancakes 1 and 2 (side A). Round 2: pancake 1 (side B) and 3 (side A). Round 3: pancakes 2 and 3 (side B).
- 3 rounds × 3 minutes = 9 minutes, instead of 12 if you cook them one pair at a time.
- Key idea: never leave the pan half empty.
🎙️ What the video says (in Chinese)
- 一口锅每次只能烙 2 张饼，两面都要烙，每面 3 分钟。烙 3 张饼，最少要几分钟？
- 先烙 1、2 号，再烙 3 号：锅空着一个位置，要烙 4 次，12 分钟。
- 不让锅空着！第 1 次：1 号正面、2 号正面。第 2 次：1 号反面、3 号正面。第 3 次：2 号反面、3 号反面。
- 只要烙 3 次，9 分钟！不让锅空着，最省时间！
✏️ Try it yourself
Same pan: how long for 4 pancakes?
Show answer
8 sides ÷ 2 = 4 rounds, 12 minutes
And for 5 pancakes?
Show answer
10 sides ÷ 2 = 5 rounds, 15 minutes
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