Four Cards

Four cards are placed in front of you on the table, each with a number on one side and a color on the other. The visible cards show 3, 8, red and brown. Which cards should you turn over in order to test the truth of the statement that if a card shows an even number on one face, then its opposite face is red?

four-cards

You’d need to turn over only the 8 and brown card. Only a card with an even number on one face and which is not red on the other face can invalidate the stated rule. If you turn over the 3 card and it’s not red, it doesn’t invalidate the rule, nor does turning over the red card and finding it has the label 3.

This test was devised by Peter Cathcart Wason and is known as the Wason selection task. Less than 10% of test subjects got it correct in two separate studies.

Posted in Brain Teasers

Fall Crop

What three or four-letter word belongs between the word on the left and the word on the right so that the first and second, and second and third words form a compound word or phrase?

For example: FOOT _ _ _ _ PARK would be BALL, or FOOTBALL and BALL PARK.

1. FALL _ _ _ CROP
2. KNEE _ _ _ SIZE
3. BOARD _ _ _ _ WAY

1. OUT – FALLOUT, OUTCROP
2. CAP – KNEECAP, CAPSIZE
3. WALK – BOARDWALK, WALKWAY

Posted in Brain Teasers

I Have Hundreds of Legs

I have hundreds of legs but I can only lean,
You make me feel dirty so you can feel clean.

What am I?

A broom.

Posted in Riddles
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Four Letters and a Fruit or Vegetable

I have four letters in my name,
I am a fruit or a vegetable,
I look like a giant green onion,
I end with the letter k.

What am I?

The leek. It has four letters, has been considered both a fruit and a vegetable, looks like a green onion and ends with the letter k.

Posted in Riddles

Two Hours Ago

If two hours ago it was as long after one o’clock in the afternoon as it was before one o’clock in the morning, what time is it right now?

9pm (or 21:00). There are 12 hours between 1pm and 1am, so 6 hours after 1am is halfway. 6 hours + 1pm equals 7pm. In order for 7pm to be 2 hours behind the current time, it must be 9pm.

Posted in Brain Teasers

I’ll Always Smile Back

If you drop me I’m sure to crack but give me a smile and I’ll always smile back

A mirror.

Posted in Riddles

It Cannot Be Seen and Weighs Nothing

It cannot be seen, it weighs nothing, but when put into a barrel, it makes it lighter. What is it?

A hole.

Posted in Riddles

He And She Both Have One Each

He and she both have one each, but every person has two. A citizen has three and a human being has four. A personality has five and an inhabitant of earth has six. What are they?

Syllables.

Posted in Brain Teasers

24 from 9, 6, 11 and 3

How do you get 24 from 9, 6, 11 and 3 using addition, subtraction, multiplication or division?

There are multiple solutions.

(6 – 3) × 11 – 9

(11 – 6) × 3 + 9

(9 – 6) × (11 – 3)

Posted in Brain Teasers

The Snooze Button

Why is it very common to have a 9 minute snooze interval on alarm clocks, why not 10 instead?

By setting the snooze time to 9 minutes, the alarm clock only needs to watch the last digit of the time. So, if you hit snooze at 6.45, the alarm goes off again when the last digit equals 4. They couldn’t make it 10 minutes, otherwise the alarm would go off right away, or it would take more circuitry.

Posted in Brain Teasers