I got one. You may need to draw this down:

There is 4 perfect circle flowerbeds meeting each other at the edge as to make a con-caved box. The Radius of the circle is 20m. Work out the area of the con-caved square and one of the circles without using pi or 3.1 or 3.

here's some

1.I'm lighter than a feather, yet most men can't hold me for very long, what am I?
2.Four men walk into a bar, why is this weird?
3.What question can someone ask all day, get different answers each time, yet they are all correct?
4.Nearly bright as the sun. Sometimes dark as space. Like a pearl on black velvet, with diamonds twinkling in my case. What am I?
5.What is so fragile it breaks when you say it?
6.(this one is famous) in the morning i walk on four legs, in the afternoon i walk on two legs, and in the evening i walk on three legs, what am I?
7.Voiceless cry, wingless flutter, toothless bite, mouthless mutter. What am I?

What is your favorite color. Or any other opinion question?

no because you can get the same answer at least twice

number 3 is what time is it exactly. Is that right?

6 is mankind through it's life like baby adult and old man

Yes both are correct

a hint for #2 is that it's more of a joke than a riddle


i heard this one as a joke, i think it was a torch

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#5 is silence.

Here's mine:
Somebody claims he can build a hidroelectric station that works with 100% efficiency. If we assume this is possible, is it good or not? Why?

I'll attempt to answer all of these.
1. breath. fairly self explanatory
2. the last three should have ducked under the bar after the first one walked into it.
3. what time is it? again, obvious.
4. the moon. because it can be dark(new moon) or bright(whole moon) and is surrounded by stars.
5. silence. when you say it, the silence is broken.
6. (yes it is) humans. crawling in the morning(infancy) two legs in the afternoon(adulthood) and with a cane in the evening(old age)
7. I actually have no Idea.

What is intelligant, but knows only two things?

something that can spell intelligent. just kidding. is it a computer because of binary code?

...sais pas, although my best guess is a computer, by the twisted logic that computer operates only two types of input, 0s and 1s.

Here's something not too difficult-
A hiker follows the same route up a mountain every morning. One day, he sees a cabin that was not there the day before. He does not enter it or look inside, but he knows upon sight of it that everyone inside is dead. Why is that?

because the axe murderer is standing outside covered in blood? (kidding)

is the cabin burnt down?

Is it because It is upside down down the mountain, as If by tornado or something?

The amount of damage to the cabin is irrelevant, his conclusion would stand either way.

Added spoilers, but yes
You win munny

Wow! I wouldnt have guessed that.

I EAT THE DOORS!!!!!!!!

I'm smart.

here are a few more.

a doctor moves out west and writes to the brother which stayed behind in the east, but the man in the east has no brother. how can this be?

a plane crashes on the border of the USA and Canada. where do you bury the survivors?

a rooster lays an egg on a roof. which way does it roll?

two American coins add up to make 30 cents and one of them is not a nickle. what are they?

Female doctor
Don't bury survivors
Roosters don't lay eggs
The other is a nickel and the first is a quarter

What is...

Yes, those two words are the riddle.

That was very close.

which one? that's two separate answers.
also What is... a word used to begin many questions
one more: What is... on second

You're on the right track but none of these is the correct answer.