Free logic puzzles for adults (with answers)

Logic puzzles are a small, satisfying workout: there is no trick and no trivia, only clues and careful thinking. This page has six puzzles that get harder as you go, from a warm-up grid to a classic balance problem. The grid, riddle and number puzzles were checked by a computer program that tried every possible answer, so each one has exactly one solution, and the coin solution was tested against every possible fake. The answers and the reasoning are at the bottom of the page.

Want something shorter? Our free Daily Mini Puzzle gives you one new maze, code or picture-math puzzle a day in a minute or two. It was written with kids in mind, but plenty of adults keep a streak going.

How to solve a logic grid

For the two grid puzzles, draw a small table on paper: names down the side, the other categories across the top. Put an X in every box a clue rules out and a circle where something must be true. When a row has only one empty box left, that box is the answer — and it often unlocks another clue. Read every clue twice; "directly to the right of" and "next to" are not the same thing.

Puzzle 1: Game night (warm-up)

Maya, Leo and Ivy each brought a different snack (popcorn, grapes or pretzels) and played a different game (chess, cards or dominoes).

1. Maya did not play chess.
2. The person who brought grapes played cards.
3. Leo played dominoes.
4. Ivy did not bring pretzels.

Who brought what, and who played which game?

Puzzle 2: Four houses on a street

Four houses stand in a row, numbered 1 to 4 from left to right. Ana, Ben, Cora and Dev each live in one. The houses are red, blue, green and yellow, and each person has one pet: a cat, a dog, a parrot or a rabbit.

1. The green house is house 1.
2. Dev lives in the blue house.
3. Ana lives directly to the right of the red house.
4. The dog lives in the red house.
5. The parrot lives next door to the yellow house.
6. Ben has the rabbit.
7. Cora does not live at either end of the street.

Who lives where, in which color house, with which pet?

Puzzle 3: Knights and knaves

On an island, knights always tell the truth and knaves always lie. You meet two islanders, A and B. A says: "We are both knaves."

What are A and B?

Puzzle 4: The secret number

I am a three-digit number. My digits add up to 13. My hundreds digit is twice my ones digit, and my tens digit is one more than my ones digit.

What number am I?

Puzzle 5: What comes next?

2, 6, 12, 20, 30, ?

Find the next number and the rule.

Puzzle 6: The fake coin

You have 9 coins that look the same. One is a fake and is slightly lighter than the others. You have a balance scale (two pans, no weights).

How can you find the fake coin in only two weighings?

Why logic puzzles are worth your time

Logic puzzles train the same habits that help at work: reading carefully, holding several facts in mind and checking an idea before you commit to it. They are also a cheap and calm hobby — a pencil and a few minutes is enough. If you share puzzles with children, a printable word search or one of our free printables makes a good side-by-side activity while you solve your own.

Answers

Puzzle 1: Game night

Leo plays dominoes (clue 3) and Maya does not play chess (clue 1), so Maya plays cards and Ivy plays chess. Grapes go with cards (clue 2), so Maya brought grapes. Ivy did not bring pretzels (clue 4), so Ivy brought popcorn and Leo brought pretzels.

Puzzle 2: Four houses

House 1 is green, so the red house is house 2 or 3 (not 4 — Ana must live to its right).

• If red were house 3, Ana would be in house 4. Dev's blue house would then have to be house 2, leaving yellow for Ana's house 4. Cora, who is not at an end, would be in the red house 3 with the dog. But the parrot must live next to yellow house 4, which is house 3 — already taken by the dog. Impossible.
• So red is house 2, with the dog, and Ana is in house 3. Dev's blue house must be house 4, which makes house 3 yellow. Cora is not at an end, so she is in house 2, and Ben is in house 1. The parrot lives next to yellow house 3 but not in dog house 2, so it is in house 4. Ben has the rabbit, and the cat goes to Ana.

Puzzle 3: Knights and knaves

A is a knave and B is a knight. A knight could never say "we are both knaves", because that would make the knight a knave. So A is a knave, and A's sentence is a lie: they are not both knaves. Since A is one, B must be a knight.

Puzzle 4: The secret number

643. Call the ones digit n. The digits are 2*n*, n + 1 and n, which add up to 4*n* + 1 = 13, so n = 3.

Puzzle 5: What comes next?

42. The gaps grow by 2 each time (+4, +6, +8, +10, +12). Another way to see it: each number is n × (n + 1) — 1×2, 2×3, 3×4 and so on, so the sixth is 6×7.

Puzzle 6: The fake coin

Split the coins into three groups of three. Weighing 1: put one group on each pan. If one side rises, the fake is in that lighter group; if they balance, it is in the group you left off. Weighing 2: from that group of three, put one coin on each pan. The lighter one is the fake; if they balance, it is the coin you left off. (We checked all nine possible fakes with a short program — two weighings always find it.)

More to try

• Rainy-day printable activities for a whole afternoon indoors.
• Daily Mini Puzzle: a new free puzzle every day.
• All guides

Feel free to share these puzzles with friends, students or a puzzle club. Please link back to this page instead of re-uploading them.