Brain Teasers for Middle Schoolers: Answers and What They Train

The best brain teasers for middle schoolers are short puzzles with one rule to find and one answer to check. This page has ten original ones for grades 5 to 8, in four types, each with its answer and the skill it trains. Practising them makes a child better at puzzles like these. We found no good evidence that it raises IQ.

Below: the puzzles, then what research says about practice, and how a brain teaser differs from the questions on a children's IQ test. Try each puzzle before you read its answer.

What are good brain teasers for middle schoolers?

Good ones have a single correct answer, need no special knowledge and reward noticing a pattern. A brain teaser for 5th graders can be a number pattern with a constant step. By 8th grade the same idea grows into puzzles with two rules or a trap. Our grade labels are a rough guide, not tested norms, and a child can start anywhere.

We wrote every puzzle below ourselves and checked each answer twice, once by hand and once by listing every case. The four types are number patterns, logic, spatial puzzles and traps. For more patterns, see our guide to number sequence puzzles.

Which number pattern brain teasers suit grades 5 to 8?

Number patterns ask a child to find the rule that turns each number into the next. Start with a constant step, then move to patterns where the gaps themselves change.

Puzzle 1 (grades 5-6). The numbers go 2, 6, 18, 54. What comes next?

Answer: 162. Each number is 3 times the one before. Trains: spotting a multiplier instead of an adder.

Puzzle 2 (grades 6-7). The numbers go 3, 5, 9, 15, 23. What comes next?

Answer: 33. The gaps are 2, 4, 6, 8, so the next gap is 10. Trains: looking at the differences between numbers, and then the pattern in those differences.

Puzzle 3 (grades 7-8). The numbers go 5, 7, 11, 19, 35. What comes next?

Answer: 67. You can add 2, 4, 8, 16 and then 32, or double each number and subtract 3. Both rules give the same answer. Trains: testing a rule two ways before trusting it.

Which logic brain teasers for kids come with answers?

Logic puzzles give a few clues and ask for the one answer that fits all of them. These are brain teasers for kids with answers you can check by listing every case.

Puzzle 4 (grades 5-6). Four friends race. Maya finishes before Theo. Ines finishes after Theo. Leo finishes before Maya. Nobody ties. Who finishes third?

Answer: Theo. The clues chain into one order: Leo, Maya, Theo, Ines. Trains: joining clues into a single ranking.

Puzzle 5 (grades 6-8). Exactly one of Ava, Ben and Cy ate the last cookie. Ava says, "Ben ate it." Ben says, "I did not eat it." Cy says, "Ava is lying." Exactly one of these three statements is true. Who ate the cookie?

Answer: Ben. If Ava ate it, Ben and Cy both speak truly, which makes two truths. If Cy ate it, Ben and Cy again both speak truly. If Ben ate it, only Ava speaks truly, so one statement is true. Trains: trying each possibility and throwing out the ones that break a rule.

Puzzle 6 (grades 7-8). A farm has only chickens and cows. Together they have 30 heads and 74 legs. How many cows are there?

Answer: 7 cows. If all 30 animals were chickens there would be 60 legs. The 14 extra legs come from cows, which have 2 more legs each, so 7 cows and 23 chickens. Check: 7 times 4 plus 23 times 2 is 74. Trains: guess, check and adjust, the start of algebra.

Which spatial brain teasers work for 6th graders?

Spatial puzzles ask a child to turn or cut shapes in their head. Here are two brain teasers for 6th graders and up. Draw them on paper if you need to.

Puzzle 7 (grades 6-8). A 3 by 3 by 3 cube is painted red on all six faces, then cut into 27 small cubes. How many small cubes have exactly two red faces?

Answer: 12. The cubes on the 12 edges of the big cube, one in the middle of each edge, show two red faces. The 8 corners show three, the 6 face centers show one and the middle cube shows none: 8 plus 12 plus 6 plus 1 is 27. Trains: sorting 3-D parts by position.

Puzzle 8 (grades 5-7). You face east. You turn left 90 degrees, then right 180 degrees, then left 270 degrees, then right 90 degrees. Which way are you facing?

Answer: North. Count right turns as plus and left turns as minus: minus 90, plus 180, minus 270, plus 90 adds up to minus 90, one left turn from east. Trains: tracking orientation and combining turns.

Which trap puzzles teach kids to check the first answer?

Trap puzzles have an obvious answer that is wrong. They teach a child to pause and test the first idea.

Puzzle 9 (grades 5-6). A school bell rings every 20 minutes, starting at 8:00. At what time does it ring for the 7th time?

Answer: 10:00. The 7th ring comes after 6 gaps of 20 minutes, which is 120 minutes. Trains: counting gaps instead of counting items.

Puzzle 10 (grades 7-8). A snail climbs a 10 m wall. Each day it climbs 3 m, and each night it slides back 2 m. On which day does it reach the top?

Answer: Day 8. The snail gains 1 m a day, but on day 8 it climbs from 7 m to 10 m and is already at the top, so it never slides back. Dividing 10 by 1 and saying day 10 is the trap. Trains: checking whether the usual rule still applies on the last step.

Do brain teasers raise a child's IQ?

We found no study showing that they do, and no trial of brain teasers or riddles on children's IQ at all. The nearest evidence is on brain training, and it says one thing clearly: practice makes you better at what you practise.

Simons and colleagues reviewed the studies cited by brain-training companies in Psychological Science in the Public Interest (2016). They found extensive evidence of gains on the trained tasks, less on closely related tasks and little on distantly related tasks or everyday thinking. Melby-Lervåg, Redick and Hulme pooled 87 working-memory training publications in Perspectives on Psychological Science (2016). Working memory improved, but there was no convincing evidence of gains in nonverbal ability, verbal ability, reading or arithmetic.

Sala and Gobet reached a similar view in Trends in Cognitive Sciences (2019): their reviews found minimal effects on general cognitive skills. Spatial skills are the best case. Uttal and colleagues pooled 217 training studies in Psychological Bulletin (2013) and found an average gain of g = 0.47, stable over time and carrying over to spatial tasks that were not trained. That supports practice on spatial puzzles, such as puzzles 7 and 8, as a way to improve spatial skills, not IQ. Our piece on whether brain training apps work covers the apps.

How are brain teasers different from IQ test questions for kids?

An IQ test is normed: a child's raw score is compared with a large sample of children of the same age, so the result is a rank. A brain teaser has no norm group, so solving one tells you nothing about rank. You can see how ranks work with the IQ percentile calculator.

Some items look alike. Number patterns and matrix puzzles appear in both. Our guide to matrix puzzles shows the shared idea, and the page on high IQ riddles explains why a clever riddle is not a test item. For sample items by age, see our IQ test questions for kids.

How do you make your own brain teaser?

Pick a rule first, such as "multiply by 3" or "turn left, then right". Build the puzzle from the rule, then check that only one answer fits. Ask a child to explain the rule out loud, because saying why an answer works is where the thinking happens. Children can write puzzles for each other, which makes the rule the point instead of the answer.

Parents can start with our kids IQ test, the IQ test for ages 8 to 12 or the test for ages 13 to 17. More logic practice is on our logic puzzles page, and adults can start at the IQ Metrics home page.

Common questions