What runs around the whole yard without moving?

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

Jenifer and Jesica are having a conversation.

Jenifer: I am definitely not over 30.
Jesica: I am 28 and you are surely 5 years older to me at least.
Jenifer: No, you are at least 29.

You are told that both of them are lying throughout in the conversation. Can you find their respective ages?

Your last good ping-pong ball fell into a narrow metal pipe embedded one foot deep in concrete.
How can you get it out undamaged, if all the tools you have are your tennis paddle, shoe laces, and plastic water bottle, which does not fit into the pipe?

If there are fifteen crows on a fence and the farmer shoots a third of them, how many crows are left?

I am five letter word that is under you.
If you remove my 1st letter, then I am over you.
If you remove my 1st and 2nd letters then I am all around you.

Who am I?

What goes up but never comes down?