What is full of holes but still holds water?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

What four weights can be used to balance from 1 to 30 pounds?

Thirty friends were on a hiking trip when they decided to enjoy the bonfire. They assembled for it and agreed to play a game. For that, they divided themselves into five teams with seven members each, forming five rows.

How did they manage to achieve this formation?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

Two friends decide to get together; so they start riding bikes towards each other. They plan to meet halfway. Each is riding at 6 MPH. They live 36 miles apart. One of them has a pet carrier pigeon and it starts flying the instant the friends start traveling. The pigeon flies back and forth at 18 MPH between the 2 friends until the friends meet.

How many miles does the pigeon travel?

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

How do you go from 98 to 720 using just one letter?

1 rabbit saw 9 elephants while going to the river. Every elephant saw 3 monkeys going toward the river. Each monkey had 1 parrot in each hand. How many animals are going towards the river?

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?