Mysterious Math

This problem can be solved by preschool children in five to ten minutes, by programmers in an hour and by people with higher education…well, check it yourself.

8809 = 6
7111 = 0
2172 = 0
6666 = 4
1111 = 0
3213 = 0
7662 = 2
9313 = 1
0000 = 4
2222 = 0
3333 = 0
5555 = 0
8193 = 3
8096 = 5
1012 = 1
7777 = 0
9999 = 4
7756 = 1
6855 = 3
9881 = 5
5531 = 0
2581 = ?

What is the missing number and why?

Two. The number is how many closed circles there are in the 4 digits. 0, 6 and 9 each have one, 8 has 2.

Posted in Brain Teasers

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

Swallowed the Dead

I’ve swallowed the dead,
Of a torn land’s end.
And I hold the remains,
Of an unknown friend

A mansion once stood,
Where I now lay,
We honor all those
Who gave us today.

What am I?

Arlington National Cemetery, the burial place of soldiers from the United States Civil War. It also houses the tomb of unknown soldiers. General Robert E. Lee’s mansion once stood on the land that is now occupied by the cemetery. And on Memorial Day in the US, we honor all those who died while serving their country’s armed forces.

Posted in Riddles
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Up a Drainpipe Down but Not Down a Drainpipe Up

What can go up a drainpipe down but not down a drainpipe up?

An umbrella.

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Which Door First?

While driving his car a man slams on the brakes when he sees, in the middle of the street, a diamond studded door, a gold door and a silver door. Which door does he open first?

His car door

Posted in Brain Teasers

Two Three Ten Sequence

If:
2 3 = 10
7 2 = 63
6 5 = 66
8 4 = 96
9 7 = __

What is the missing number?

f(n, m) = (n + m) × n

e.g. f(2, 3) = (2 + 3) × 2 = 10

Hence, f(9, 7) = (9 + 7) × 9 = 144

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Surf, School, Room

What word can be added before or after these words to make a new word or phrase?

Surf, School, Room

Board. Surf board, school board (or maybe boarding school), board room.

Posted in Riddles

A Black Dog Sleeping

A black dog is sleeping in the middle of a black road that has no streetlights and there is no moon. A car coming down the road with its lights off steers around the dog. How did the driver know the dog was there?

It was daytime.

Posted in Riddles

Why This Particular Order?

Why are these letters grouped in this particular order?

1) DFGHLPRU
2) KSTV
3) CO
4) AIW
8) MN

The letters are grouped by the number of U.S. States beginning with that letter. M and N are tied for each starting eight states.

Posted in Brain Teasers

At Birth It Can’t Start Nor By Death Is It Ended

More precious than gold, but cannot be bought,
Can never be sold, only earned if it’s sought,
If it is broken it can still can be mended,
At birth it can’t start nor by death is it ended.

Friendship. It is more precious than gold to have a genuine friend, and true friendship cannot be bought or sold, only earned. When a friendship is broken it can be fixed and infants aren’t able to make friends until they’re older, but death can’t end it. Love doesn’t work as an answer because a friendship requires two people to interact, while parents love their children as soon as they’re born.

Posted in Riddles