Which is heavier: a ton of bricks or a ton of feathers?

I organized a small get together at my home.
In the party , i have a barrel with some whiskey in it.

Suddenly Guest 1 say 'I bet this barrel of whiskey is more than half full'.
'No, it's less than half full' Guest 2 replied.

I don't have any measuring instrument and without removing whiskey from it , how can i determine which of the guest is right ?

What do you get if you add 2 to 100 four times?

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

Can you count the number of quadrilaterals in the picture below?

Three men in a cafe order a meal the total cost of which is $15. They each contribute $5. The waiter takes the money to the chef who recognises the three as friends and asks the waiter to return $5 to the men.

The waiter is not only poor at mathematics but dishonest and instead of going to the trouble of splitting the $5 between the three he simply gives them $1 each and pockets the remaining $2 for himself.

Now, each of the men effectively paid $4, the total paid is therefore $12. Add the $2 in the waiters pocket and this comes to $14. Where has the other $1 gone from the original $15?

Can you place six X (crosses) in below board without making three in a row in any way ?

You can hear me, but you can't touch or see me.

What am I?

There are 3 apples in the basket and you take away 2. How many apples do you have now?

Identify the 10 differences between the two given pictures.