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Brain Games · Logic
Today's Easy puzzle: 4 people, 3 categories. Everyone gets the same puzzle today.
In short
Logic puzzles are problems you solve by reasoning from clues, with no maths or trivia needed. Our logic grid puzzles give you a few people and their facts; you tick and cross a grid until only one answer fits. Every puzzle here has exactly one answer, and you never need to guess.
Below: the daily puzzles, six solving techniques, a worked example, classic brain teasers with answers, and how logic relates to IQ.
How to play
Pick a mode at the top and press Start. Tap a box once for ✗ (no), twice for ✓ (yes). The answer table under the grid fills itself in as you go.
Deduction, with the same puzzles for everyone each day.
Deduction at the level you choose.
How logic grids work, one step at a time.
The levels
Bigger grids and more kinds of clue. The bars show how many boxes each grid has, from 27 to 250.
| Level and clues | Grid |
|---|---|
| Learn: is, is not | 3 × 3 |
| Easy: + either/or | 3 × 4 |
| Medium: + older/younger, neither/nor | 4 × 4 |
| Hard: + exact gaps | 4 × 5 |
| Expert: everything | 5 × 5 |
Hard and Expert may need one “what if”: suppose a box is ✓, and the clues soon contradict it. Never more than one step deep.
How to solve
Our solver uses exactly these, and so can you:
A worked example
Ana, Ben and Cara each have one pet (cat, dog or parrot) and one drink (tea, coffee or juice). Who has what?
Answer: Ana has the cat and tea, Ben the dog and coffee, Cara the parrot and juice.
Classic logic puzzles
Old favourites, told in our own words. Try each one before you open the answer.
A farmer must take a wolf, a goat and a cabbage across a river. The boat holds the farmer and one of them. Left alone, the wolf would eat the goat, and the goat would eat the cabbage. How does everything get across?
Take the goat across first. Go back, take the wolf across, and bring the goat back with you. Leave the goat, take the cabbage across to the wolf, then go back for the goat. Seven crossings in all.
Three boxes are labelled Apples, Oranges, and Apples and oranges. Every label is wrong. You may take one fruit from one box without looking inside. How do you label every box correctly?
Take a fruit from the box labelled Apples and oranges. Its label is wrong, so it holds one kind only: say you pull out an apple, so it is the apples box. The box labelled Oranges can’t hold oranges, and the apples are found, so it holds both. The last box holds oranges.
One door leads out and the other does not. One guard always tells the truth, the other always lies, and you don’t know which is which. You may ask one guard one question. What do you ask?
Ask either guard: “Which door would the other guard say leads out?” Then take the other door. The liar lies about the honest guard’s answer, and the honest guard truthfully reports the liar’s lie, so both point to the wrong door.
On an island, knights always tell the truth and knaves always lie. You meet A and B. A says: “We are both knaves.” What are A and B?
A is a knave and B is a knight. If A were a knight, the sentence would be true, and A would be a knave: impossible. So A lies, which means they are not both knaves, so B is a knight.
Four people must cross a bridge at night with one torch. They take 1, 2, 5 and 10 minutes. At most two cross at once, at the slower one’s speed, and someone must bring the torch back. What is the fastest time?
17 minutes. 1 and 2 cross (2), 1 comes back (1), 5 and 10 cross (10), 2 comes back (2), 1 and 2 cross (2).
Three switches downstairs control one bulb upstairs. You may go upstairs only once. How do you find the right switch?
Turn on switch 1 for a few minutes, then turn it off and turn on switch 2. Go up. If the bulb is lit, it is switch 2; if it is off but warm, switch 1; if it is off and cold, switch 3.
Each of two ropes burns in exactly 60 minutes, but unevenly. How do you measure 45 minutes?
Light rope A at both ends and rope B at one end. A burns out after 30 minutes. Then light the other end of B: it burns out 15 minutes later, 45 minutes in all.
Nine coins look the same, but one is heavier. With a balance scale, how do you find it in two weighings?
Weigh 3 against 3. If they balance, the heavy coin is in the last 3; if not, it is on the heavier side. Then weigh 1 against 1 from that group: the heavier one is it, or the third coin if they balance.
Types of puzzle
The main types of logic puzzles belong to a few families. All of them are solved by reasoning from rules, never by guessing.
Match people to facts from clues, marking a grid with ticks and crosses. This is the game on this page.
Bigger grids, often five houses with five facts each, solved the same way with more clues.
In knights and knaves puzzles, some characters always tell the truth and some always lie. You work out who is who from what they say.
Get everyone across under rules about who can be left with whom. The classic is the wolf, the goat and the cabbage.
Sudoku and kakuro place numbers by rules. Sudoku needs no arithmetic at all: only logic about where each digit can go.
Nonograms fill cells from number clues on each row and column, and a picture appears when you finish.
Skills
Combining facts to reach a new one: A is B, B is not C, so A is not C.
Keeping several clues and their consequences in mind while you mark the grid.
Reading each clue exactly: “is older than” and “is 2 years older than” say different things.
And IQ
Partly. Logic grids test deductive reasoning: applying rules you are given. IQ tests lean more on inductive reasoning, finding the rule yourself, as in a matrix puzzle. Both belong to the IQ area called fluid reasoning.
Solving more puzzles makes you better at puzzles; there is little evidence it raises IQ. For timed reasoning questions, try our logical reasoning test, or take the online IQ test for a full score.
The five areas of a modern IQ test
The five primary index areas of the WISC-V (children, 2014) and the WAIS-5 (adults, 2024). See WAIS-5 index scores explained.
FAQ
A puzzle where each person has exactly one item from every category. Clues rule pairs in or out, and you mark them in a grid with ✗ (no) and ✓ (yes) until every person has their match.
Yes. A puzzle is kept only if our solver finishes it using the steps its level allows, which proves there is exactly one answer.
No. Every puzzle can be solved by deduction alone. Hard and Expert may need one “what if” at most: suppose a box is ✓, and the clues soon contradict it.
✗ means the two items do not belong to the same person; ✓ means they do. Tap a box once for ✗, twice for ✓, and a third time to clear it.
When you place a ✓, Auto ✗ fills the rest of its row and column in that grid with ✗, because each person has only one item of each kind. You can switch it off.
At midnight where you are. Everyone gets the same three puzzles for the same date, and the last 30 days stay playable.
Yes. Print opens the puzzle with its clues and an empty grid, with the answer on a second page.
They are the same kind of puzzle. The zebra puzzle, also called Einstein’s riddle, is one famous example with five houses and fifteen clues; a logic grid is the usual way to solve it.
There is no evidence that he did, or that Lewis Carroll did. A version was published in Life International magazine on 17 December 1962, with the solution in March 1963.
There is no good evidence that they do. They make you better at logic puzzles and are good practice in careful reasoning. A full IQ test measures reasoning across many kinds of questions.
By the same solver that checks each puzzle. A hint first shows where to look, then explains the step in one sentence, and only then marks it for you. Hints are counted on your result.
They are good practice in careful thinking, and fun to share. There is little evidence that they raise IQ or everyday memory; mostly they make you better at puzzles like them.
Yes. After you solve a puzzle, send the link: your friend gets the very same puzzle and sees both times.
Yes. It is free to play, with no signup, and your progress stays in your browser.
Sources
The full picture
Each game looks at one skill. The IQ test brings speed, reasoning and memory together in one score, with your percentile and a certificate.
