creouts
A three-row number pyramid with 28 on top, 13 and 15 below, and 3, 5 and 5 along the bottom, beside the cover of Escape the Sleepwalking Town.

Field Notes

Catching Yawns: Doubling, Halving and a Counted-Twice Brick

2 min read
  • How to play
  • Mental math
  • Gamebooks

Yawns are catching, and so is the lock called Catching Yawns in Escape the Sleepwalking Town. Its rule: every brick is the two bricks below it added together, but a brick wearing a ×2 yawn badge is counted twice. Doubling goes up. Halving comes back down.

A made-up example

The top is 28. The bottom row is 3, a missing brick and 5. The missing brick wears the yawn badge, so it counts twice wherever it is added.

Start

What we know

Top 28, bottom 3, ? and 5. The middle bottom brick yawns, so it is counted twice.

Step 1

Build the middle row with the missing brick

The left middle brick is 3 + the yawner counted twice. The right middle brick is the yawner counted twice + 5. Call the yawner x: 3 + 2x and 2x + 5.

Step 2

Count it again at the top

The top is (3 + 2x) + (2x + 5) = 8 + 4x. The yawner is counted four times in all: twice in each middle brick.

Step 3

Take away the known and halve twice

28 − 3 − 5 = 20. That is four yawners. Halve it: 10. Halve again: 5. The yawner is 5.

Step 4

Check

3 + 5 + 5 = 13 and 5 + 5 + 5 = 15 (the yawner counted twice each time). Then 13 + 15 = 28.

Halving in your head

Halving is easier than it looks if you split the number into friendly parts.

  • Halve tens and ones separately. Half of 74: half of 70 is 35, half of 4 is 2, so 37.
  • Halve hundreds first. Half of 136: half of 100 is 50, half of 36 is 18, so 68.
  • Halve twice for a quarter. A quarter of 20 is half of 10, which is 5.
  • Check by doubling. 37 doubled is 74. Always true.

How a page looks in the book

The New Lock page of Escape the Sleepwalking Town explaining Catching Yawns, with a puzzle and its solved version side by side.
The page that teaches Catching Yawns.
A chamber page of Escape the Sleepwalking Town showing a Catching Yawns lock with yawn badges, and a Next Door box.
A Catching Yawns chamber, as printed.

A low-resolution page from Escape the Sleepwalking Town, so you can see the layout. Nothing on it is solved.

Books mentioned

Escape the Sleepwalking Town cover

Escape the Sleepwalking Town

A comic puzzle adventure gamebook up nine locked streets to the Wake-Up Pyramid, with 15 kinds of lock and true sleep facts. Catching Yawns is one of them.

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