Free Mensa IQ Critical Thinking Practice Test Flashcards

All roses are flowers. Some flowers fade quickly. Therefore:

Answer: B. Some roses may fade quickly

This is a syllogism. We know all roses are flowers, and some flowers fade quickly. It's possible (but not certain) that some of those fading flowers are roses. We cannot conclude all roses fade quickly, only that some roses may.

If it is true that 'No X is Y' and 'All Z is X', which must be true?

Answer: B. No Z is Y

If no X is Y, and all Z is X, then Z is a subset of X. Since nothing in X is Y, nothing in Z (being part of X) can be Y. Therefore 'No Z is Y' must be true.

A study shows students who eat breakfast score higher on tests. A teacher concludes breakfast causes better test scores. What flaw exists in this reasoning?

Answer: B. Correlation does not imply causation

The classic logical flaw: correlation does not imply causation. Students who eat breakfast may also have other habits (better sleep, stable home environment) that cause higher scores. The relationship is correlational, not necessarily causal.

Five people sit in a row. Anna is not at either end. Ben is to the right of Anna. Clara is at the leftmost seat. Dana is between Clara and Anna. Who is at the rightmost seat?

Answer: C. Eric

Clara is at position 1 (leftmost). Dana is between Clara and Anna. So the order so far: Clara(1), Dana(2), Anna(3). Ben is to the right of Anna, so Ben is at 4 or 5. Eric takes the remaining spot. Since Anna is not at an end and Ben must be right of Anna, Ben is at 4 and Eric is at 5 (rightmost).

Which argument contains circular reasoning?

Answer: B. This book is trustworthy because the author says it is accurate

Circular reasoning (begging the question) occurs when the conclusion is used as a premise. 'The book is trustworthy because the author says it is accurate' uses the author's credibility as proof of the author's credibility — the conclusion supports itself.

Three friends each prefer a different sport: football, tennis, or swimming. Alex doesn't like water sports. Blake prefers racket sports. Who likes football?

Answer: A. Alex

Blake prefers racket sports = tennis. Alex doesn't like water sports = not swimming. Since Blake has tennis, Alex must choose between football and swimming — but Alex dislikes water sports, so Alex likes football. Charlie likes swimming.

What is the logical conclusion if: 'All politicians are public figures' and 'Some public figures are dishonest'?

Answer: C. Some politicians may be dishonest

All politicians are public figures (politicians ⊆ public figures). Some public figures are dishonest. The dishonest public figures may or may not overlap with politicians. Therefore 'some politicians may be dishonest' is the only valid conclusion.

A man is looking at a photograph and says, 'Brothers and sisters I have none, but that man's father is my father's son.' Who is in the photograph?

Answer: C. The man's son

Since he has no brothers or sisters, 'my father's son' = himself. So 'that man's father is me.' Therefore the man in the photograph is his own son.

Which of the following best identifies the flaw: 'We should not trust John's opinion on the new policy because he dresses oddly.'

Answer: B. Ad hominem

Ad hominem is attacking the person rather than their argument. Dismissing John's policy opinion based on his appearance is irrelevant to the validity of his argument — this is a classic ad hominem fallacy.

If all Bloops are Razzles and all Razzles are Lazzles, are all Bloops definitely Lazzles?

Answer: A. Yes

This is transitive reasoning. Bloops ⊆ Razzles, and Razzles ⊆ Lazzles. Therefore Bloops ⊆ Lazzles. All Bloops are definitely Lazzles.

In a room, there are 4 people. Each person shakes hands with every other person exactly once. How many handshakes occur?

Answer: B. 6

The number of handshakes = combinations of 4 people taken 2 at a time = 4!/(2!×2!) = 6. Each unique pair (A-B, A-C, A-D, B-C, B-D, C-D) = 6 handshakes.

What logical error is: 'Either you support this new law or you hate freedom.'

Answer: C. False dilemma

This is a false dilemma (false dichotomy) — presenting only two options when more exist. One could support freedom while opposing this specific law for other valid reasons. The argument artificially limits the choices.

A clock shows 3:15. What is the angle between the hour and minute hands?

Answer: B. 7.5°

At 3:15, the minute hand is at 90° (pointing to 3). The hour hand: at 3:00 it is at 90°, but by 3:15 it has moved 15/60 × 30° = 7.5° further. So the hour hand is at 97.5°. The angle between them = 97.5° - 90° = 7.5°.

Tom is taller than Sam. Sam is taller than Mike. Pete is shorter than Mike. Who is the tallest?

Answer: C. Tom

The height order from the clues: Tom > Sam > Mike > Pete. Tom is the tallest.

Which conclusion is valid? Premise 1: If it rains, the ground is wet. Premise 2: The ground is wet.

Answer: B. It may or may not have rained

This is the fallacy of affirming the consequent. The ground being wet doesn't confirm rain — a sprinkler could have caused it. The valid conclusion is only that it may or may not have rained.

A bat and ball cost $1.10 together. The bat costs $1 more than the ball. How much does the ball cost?

Answer: B. $0.05

Let ball = x. Bat = x + $1. Together: x + (x + 1) = 1.10. So 2x = 0.10, x = $0.05. The ball costs 5 cents. (Many people intuitively say $0.10 but that's wrong — the bat would then cost $1.10 and total $1.20.)

Six people are in a race. The positions are 1st through 6th. Maya finished before Jess but after Kyle. Dan finished last. Sam finished before Maya. Who finished first?

Answer: D. Cannot be determined

We know: Kyle > Maya > Jess, and Sam > Maya, and Dan is last. Both Kyle and Sam are before Maya, but their relative order to each other is not specified. Either Kyle or Sam could be first — it cannot be determined from the given clues alone.

Which of the following is an example of a hasty generalization?

Answer: B. I met two rude people from City X, therefore everyone from City X is rude

A hasty generalization draws a broad conclusion from a small or unrepresentative sample. Meeting two rude people and concluding everyone from that city is rude is a classic hasty generalization.

What comes next in the logical sequence: 1, 4, 9, 16, 25, ?

Answer: B. 36

These are perfect squares: 1²=1, 2²=4, 3²=9, 4²=16, 5²=25. The next is 6²=36.

If you rearrange the letters CIFAIPC, you get the name of a(n):

Answer: B. Ocean

Rearranging CIFAIPC gives PACIFIC — the name of an ocean (Pacific Ocean).