How to Solve a Logic Puzzle

If you're new to grid-based logic puzzles, this tutorial will teach you the basics. Start with the "Introduction" first, then move on to the tutorials discussing specific clues or solving methods. Each tutorial contains a number of different slides - you can advance to the next slide by clicking "Next slide" at the bottom of each page, or by using the circled numerical links below each slide. Choose your specific tutorial from the list below to get started.

  • Introduction
  • True and False Clues
  • Multi-Elimination Clues
  • Neither/Nor Clues
  • Either/Or Clues
  • Greater/Lesser Than Clues
  • Unaligned Pair Clues
  • Transpositions
  • Parallel Cross Eliminations
  • Skewed Cross Eliminations
  • Pseudo-True Pairs (Aligned)
  • Pseudo-True Pairs (Staggered)
  • Transitive Relationships (Either/Or)
  • Transitive Relationships (Unaligned Pair)
  • Comparative Relationships
  • Trial and Error
  • Taking Notes
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    Parallel Cross Eliminations


    • Slide #1

      Cross-elmination is an advanced solving method that comes in two flavors: geometrical and non-geometrical. It is a grid-only solving method, meaning it can be utilized without any need to refer to the clues. Although both "flavors" work in the same way and for the same reasons, geometrical cross-elimination is somewhat easier to pick out visually from a grid. Non-geometrical cross-elimination is a bit harder to spot.

      In the first five slides of this tutorial we'll discuss Geometrical Cross-Elimination using the pre-filled grid to your left. Nine boxes have been X'd out. Using nothing but geometrical cross-elimination, we'll be able to X out two more.


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    • Slide #2

      The goal of cross-elimination is to find a subcolumn or subrow which has only a few (2 or 3) remaining options, and then see if any other subcolumns/subrows exist where all of those remaining options have already been eliminated.

      In this case, let's look at the "Peters" column by way of months, in the top-left portion of the grid. (This section has been highlighted in yellow in the grid to your left.) February, March and April have been eliminated for Peters, meaning Peters must be either January or May.


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    • Slide #3

      For the purposes of this example, we'll now compare the Peters column (yellow) to the X-ray column (green). Notice how the X-ray column is practically a mirror-image opposite of the Peters column.


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    • Slide #4

      We call these types of cross-elimination columns/rows "geometrical" because they occur in a horizontal or vertical alignment with each other, and are therefore fairly easy to spot. In your mind, try to "lift up" the X-ray column and move it to the left until it overlays the Peters column. If all five options in the column are then X'd out, that's a valid cross-elimination.

      Now that we've found it, what can we do with it?


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    • Slide #5

      Since Peters can only be January or May, and X-ray cannot be either January or May, we now know that Peters and X-ray can never be paired together. That gives us an X in the Peters/X-ray box near the bottom of the grid (blue row).

      Not too hard, right? Now it's your turn - advance to the next slide and see if you've got the hang of it.


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    • Slide #6

      This is the exact same grid as in the previous slide, just with the coloring and arrows removed. There is one more geometrical cross-elimination possible on this grid. Can you find it?


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    • Slide #7

      Did you find it?

      March can only be Lee or Rhodes, but Theros can be neither Lee nor Rhodes - therefore, March cannot be Theros and we can put an X in the yellow square to the top-right of the grid. This time it was a vertical cross-elimination, but all the principles remain the same.

      Now that you've tackled geometrical cross-eliminations, let's roll up our sleeves and try the slightly harder non-geometrical cross-eliminations.


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