True and False Clues in Logic Grid Puzzles
Part 1 of 6 of How to Solve Logic Grid Puzzles.
The simplest clues state a fact outright. A true clue says two items go together. A false clue says they don't.
A true clue
Clues don't have to be used in order, and a plain fact is the easiest place to start.
Clue 2. The insect that sold for $280 was the 9th lot.
This clue is about a price and a place in the order, so it belongs in the top-right grid. Find the square where the $280 row meets the 9th column, and mark it with a circle.
Now apply the two rules. The $280 butterfly had only one place in the order, so it wasn't the 2nd, 3rd, 4th or 6th lot. And only one butterfly was the 9th lot, so it didn't sell for $250, $260, $270 or $290. That's eight X's from a single clue.
In the app, Auto-X adds these X's for you as soon as you mark a match.
Notice that the X's stop at the heavy line. The $280 row carries on into the winners grid on its left, but clue 2 says nothing about who won that butterfly, so those squares stay empty for now.
A false clue
Clue 5. The butterfly won by Marco didn’t sell for $270.
A false clue rules out a single square. Find where the Marco column meets the $270 row, and mark it with an X.
One X doesn't look like much, but this one ends up deciding the last step of the puzzle.
False facts are also hidden inside other kinds of clue. The next parts show where to find them.
When only one square is left
X's matter because of the first rule. Every row and column of a small grid needs exactly one circle, so once four of its five squares hold an X, the fifth must be the circle. Most of a puzzle is solved this way, and the last part has several examples.
Practise on puzzles like these in our Logic Grid Puzzles app, for iPhone, iPad, Android and Amazon Fire.