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Sandy Wood
Brain Game: Line Up!
by Sandy Wood - June 19, 2009 - 7:30 AM

bloghead_braingames.jpg

Study this chalkboard mathematics equation for today’s Brain Game:

5 + 5 + 1 = 5 4 6

Your goal is to move certain lines to make the two sides of the equation equal. And I want you to do it not once, not twice, but three times. First, solve for puzzle #1, then (referring back to the original image) solve for puzzle #2, and then puzzle #3. Good luck!

PUZZLE #1: Make both sides of the equation equal by
adding a single straight line to the left side of the equation.

PUZZLE #2: Make both sides of the equation equal by
removing a single straight line from the right side of the equation.

PUZZLE #3: Make both sides of the equation equal by moving one straight line
from the left side of the equation to the right side of the equation.

Here are three possible SOLUTIONS.
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Comments (7)

  1. Ahhhh… that’s the same answer I was getting, but then I reread the instructions and I thought we were supposed to be using the solution for #1 as the start for #2, and the solution for #2 as the start for #3. Then my brain imploded from thinking too much with too little caffeine. Thanks…

    posted by John on 6-19-2009 at 11:16 am

  2. Understood, John. To be clearer, I added a parenthetical phrase to the instructions to ensure that readers refer back to the original image when solving each of the three puzzles. Thanks!

    posted by Sandy Wood on 6-19-2009 at 11:27 am

  3. Sorry Sandy, your solution to number 3 is bogus. Your instructions do not allow rotating the line. You’d wind up with 5416 on the right.

    posted by PartiallyDeflected on 6-19-2009 at 12:57 pm

  4. Hmmmm… the instructions don’t disallow rotating the lines. To specifically say “rotating is allowed” would have been too much, I think. Tough call, though!

    posted by Sandy Wood on 6-19-2009 at 1:24 pm

  5. I guess I could have said “remove a line from the left side and add a line to the right side” — but it just seemed simpler to say “move” it.

    posted by Sandy Wood on 6-19-2009 at 1:28 pm

  6. The directions were fine Sandy. Rotation is a form of movement. I suppose one could write explicit rules for all puzzles and remove all creativity and independent thought. That would be fun!

    posted by SteveO on 6-19-2009 at 2:17 pm

  7. I went about solving #1 and #2 in a different route. I took the liberty of adding the “+” sign to the sum of both sides of the equation. They’re assumed to be positive, right? I then subtracted 267.5 (the average of the 2 sums) to get “-267.5 = 267.5″. I simply added my line to the left to flip the negative sign into a positive one. Unfortunately, I couldn’t get my sign flipping trick to work on #3. I felt my math trick of adding/ subtracting the same number from both sides was fair. But, if the instructions had “only” in them, it would have been a different story.

    posted by Blake on 6-19-2009 at 5:35 pm

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