Loud Linda

Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice, and also participated in anti-nuclear demonstrations.

Which is more probable?

1) Linda is a bank teller.
2) Linda is a bank teller and is active in the feminist movement.

1) Linda is a bank teller.

Most people guess number two, but the probability of two events occurring together is always less than or equal to the probability of either one occurring alone. This problem is known as the Conjunction Fallacy.

Posted in Riddles

What is the Five Digit Number?

What 5-digit number satisfies the following requirements?

1. No zeroes
2. First two digits are the same
3. Fourth digit is twice the first
4. Last digit is twice the third
5. Sum of all digits is 18

33264.

There are several ways of solving this. One way is to represent each spot with a letter, A – E.

Then you have these equations:

A = B
D = 2 * A
E = 2 * C
A + B + C + D + E = 18

By simplifying, you get:

4 * A + 3 * C = 18

Plug in values for A and C to find that A = 3 C = 2.

Posted in Brain Teasers

The Bookworm

A bookworm eats from the first page of an encyclopedia to the last page in a straight line. The encyclopedia consists of ten 1000-page volumes and is sitting on a bookshelf in the usual order. Not counting covers, title pages, etc., how many pages does the bookworm eat through?

        __                             __
      B|  |                           |  |F
      A|1 |...........................|10|R
      C|  |                           |  |O
      K|  |                           |  |N
       |__|                           |__|T
      -------------------------------------

On a book shelf the first page of the first volume is on the “inside”, so the bookworm eats only through the cover of the first volume, then 8 times 1000 pages of Volumes 2 – 9, then through the cover to the 1st page of Vol 10 for a total of 8,000 pages.

Note: The question asks how many pages, not how many sheets of paper.

Posted in Brain Teasers

Always Hungry, Must Be Fed

I am always hungry,
I must always be fed,
The finger I touch,
Will soon turn red

Fire

Posted in Riddles

Finding Rhymes in Categories

Find rhymes for each set of words so the first is a category and the rest are items in the category.

For example, LOYALTY: spring, clean, rinse → ROYALTY: king, queen, prince

1. LOIN: mortar, climb, pickle
2. SQUISH: famine, search, doubt
3. GILDING: radium, Bose, hassle
4. THYME: surgery, girder, scrutiny

1. COIN: quarter, dime, nickel
2. FISH: salmon, perch, trout
3. BUILDING: stadium, mosque, castle
4. CRIME: perjury, murder, mutiny

Posted in Brain Teasers

Head, Tail, Brown and No Legs

What has a head, a tail, is brown, and has no legs?

A penny.

Posted in Riddles

Working With Something In Its Eye

What always works with something in its eye?

A needle. Thread goes in the eye of the needle when you sew. If you sew…

Posted in Riddles

Which Are True and Which Are False?

A. When a car is driven forwards the wheels rotate counter-clockwise.
B. If a clock is put forward 1 1/4 hours the minute hand moves through 450°
C. When a clock reads 4.10 the acute angle between the hands is exactly 60°

A. False – The near-side wheels rotate counter-clockwise, but the far-side wheels rotate clockwise.
B. True
C. False – The acute angle is a little more than 60° because by the time the minute hand reaches 10, the hour hand will have moved slightly past the 4.

Posted in Brain Teasers

Groups of Creatures

These are names given to groups of creatures or things, but they have been scrambled. What is the correct arrangement?

Colony of Birds
Horde of Spiders
Den of Wild Pigs
Clutter of Crows
Nest of Snakes
Park of Elks
Doylt of Ferrets
Gang of Machine Guns
Business of Swine
Volery of Artillery
Hover of Gnats
Drift of Frogs

Colony of Frogs
Horde of Gnats
Den of Snakes
Clutter of Spiders
Nest of Machine Guns
Park of Artillery
Doylt of Swine
Gang of Elks
Business of Ferrets
Volery of Birds
Hover of Crows
Drift of Wild Pigs

Posted in Brain Teasers

One Six Seven Nine to Twenty Four

Given the numbers 1, 6, 7 and 9, find an equation that equals 24. You may only use each digit once.

91 – 67 = 24 or
(9 – 6) x (7 + 1) = 3 x 8 = 24 or
6 x √9 + 7 – 1 = 18 + 6 = 24

Posted in Brain Teasers