How Can Four Be Half of Five?

How can the number 4 be half of FIVE?

Beginning with FIVE, take away the F and E (half of the letters), leaving IV, which is the Roman numeral for four.

Posted in Brain Teasers

Only Self-Enumerating Number

What is the only self-enumerating number in English?

Four. The number four has four letters, making it self-enumerating. Interestingly, there are no self-enumerating numbers in French.

Posted in Brain Teasers

Lying On Certain Days of the Week

Angel lies on Mondays, Tuesdays and Wednesdays but tells the truth the rest of the week.

Brenda lies on Thursdays, Fridays and Saturdays, but tells the truth every other day.

Angel says, “Yesterday I was lying.”

Brenda replies, “So was I.”

What day was it?

Thursday.

Putting the information in a table makes it easier to solve. We’ll use A for Angie, B for Brenda, T for truth and F (false) for lying.

  S M T W Th F S
A T F F F T T T
B T T T T F F F

To begin with, there aren’t any days where both of them told the truth and lied the day before, so we know one of them must be lying.

So we have two options, either Angel is lying or Brenda is.

Option 1. Angel is lying.

In order for this to be the case, she needs to be lying today and telling the truth yesterday, so we need two days in a row with T F. And if Brenda is telling the truth, she would need two days with F T. That means we’re looking for two days that have

Angie:  T F
Brenda: F T

Option 2. Brenda is lying.

This is just the reverse of the above, so we need to find:

Angie:  F T
Brenda: T F

The only day that matches either of the two options is Thursday, and it’s option 2. Brenda is the liar.

Posted in Brain Teasers

Halo of Water, Tongue of Wood

Halo of water, tongue of wood
Skin of stone, long I’ve stood.
My fingers short reach to the sky
Inside my heart men live and die.

A castle.

Posted in Riddles

854917632

What is special about the number 854917632?

It is the numbers from 1 to 9 in alphabetical order.

Eight
Five
Four
Nine
One
Seven
Six
Three
Two

Posted in Riddles

Three Kinds of Apples

Three kinds of apples are mixed randomly in a box. How many apples must you take out to be sure of having at least two apples of one kind?

Four. If the apples are A, B, and C, it’s possible that you could take out one A, one B and one C with three apples, but the fourth apple must be one of the three kinds.

Posted in Brain Teasers

Can’t Keep It Until You’ve Given It

You can’t keep this until you have given it.

A promise (or your word).

Posted in Riddles

Five Items In a Tennis Court

We’re five little items of an everyday sort. You’ll find us all in a tennis court. What are we?

The vowels. The phrase “a tennis court” contains all five vowels sorted in alphabetic order: a, e, i, o, u.

Posted in Riddles

Which Do You Light First?

You have a single match and are in a pitch black room with a candle, an oil lamp and a gas stove. Which do you light first?

The match.

Posted in Brain Teasers

I See Much But Change Little

I see much but change little,
I am firm, irresolute,
Powerful but gentle,
I can rip apart mountains,
Yet be moved by gentle stirrings,
I am valued and wasted,
I am life itself,
And I give life to others.

What am I?

A tree. A tall one can see long distances but don’t change much. They are strong and powerful, and the roots of a tree can slowly tear apart a mountain. The gentle stirrings of the wind can blow their branches and leaves. Trees are valuable as they provide wood and paper, but they are also wasted. And lastly, trees, like all plants, provide us with life-giving oxygen.

Posted in Riddles