Puzzles index

Some simple puzzles

Here are some simple puzzles and jokes which I like!

First, a joke: A foreman was in charge of a building site, and he was convinced that one of the workman was stealing material from the site. Every day, the workman wheeled a wheelbarrow out of the site with some sacking in it. Every day, the foreman carefully searched the barrow, and the man, but could find nothing. Finally, the building work was over, and they left the site. Later on, the foreman met the workman, and they chatted about old times. The foreman ended up by saying, "Look, I know you were stealing something! It's sending me mad. I won't do anything about it, but please tell me what it was!"

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A puzzle: A lorry (or truck) was got itself jammed underneath a bridge. It can't manage to get itself out again. What should the driver do?

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Look at the top row of your keyboard. What is the only 10 letter word you can spell? (You are allowed to repeat letters.)

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Now for a paradox: If you can only answer Yes or No, is No the answer to this question?

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Some 'sucker' puzzles

These should be easy to work out, but for some reason, people give the wrong answer.

A bat and ball cost 1.10 and the difference between them is 1. How much does each cost? Click to find the

Lily pads on a lake double their area each day. They cover the lake in 48 days. How long do they take to cover half the lake? Click to find the

It takes 5 machines 5 minutes to make 5 widgets. How long does it take 100 machines to make 100 widgets? Click to find the

As a further comment on the last problem, sometimes at work managers put more people on a project to get it finished quicker. We used to say (under our breath) "Make a baby in one month. Use nine women if necessary."

An old, old puzzle

This one is from my childhood: Think of a number.
Add 5
Multiply by 2
Subtract 4
Divide by 2
Take away the number that you first thought of
The answer is always 3.
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The clock paradox

There are two clocks. These are the old fashioned clockwork clocks which never worked very well. One clock loses 5 minues every day, so each day it tells the time 5 minutes later than it really is. The other clock is broken and doesn't work at all, always showing the same time. Which clock tells the time better?

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The goldfish principle

I don't know if this story is true, but it's a good story!

When the Royal Society was formed, King Charles II set them a problem. Imagine a bowl full of water. Now put a goldfish into the bowl. Why doesn't it overflow?

The scientists took a long time thinking about this. They considered one theory, then another, but none seemed right.

How did they find out?

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Simple IQ test

There are four cards which each have a letter on one side and a number on the other. You can only see one side of the four cards, which show D K 3 7.

Someone tells you that every card with D on one side has 3 on the other. What is the fewest number of cards which you can turn over to find out whether this statement is true or not? And which cards are they?

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Language rather than numbers

Here are two ideas to do with language rather than numbers, but using numbers.

Twelve plus one = eleven plus two

Well, of course it is! But 'TWELVE PLUS ONE' is an angram of ELEVEN PLUS TWO'. Which is satifying, somehow.

(12 + 144 + 20 + 3√4) / 7 + 5 x 11 = 92 + 0

This is also accurate. But it is also a limerick:

A dozen, a gross and a score
Plus three times the square root of four
Divided by seven
Plus five times eleven
Is nine squared and not a bit more!

Lightning calculator

It's harder to multiply by 7 than, for example, 2, isn't it! Well, try this: Think of a number less than a thousand (a 3 digit number). I can multiply that by 7, then 11, then 13, in my head, super fast, and give the right answer!

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A sequence

What is next in this sequence?

1,2:O    2,3:T    3,4:R

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The sequence continues as well. When does it stop?

What is right?

Two wrongs don't make a right, but three rights make a left.