Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?

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

Make the seating arrangement of 10 children in such a way that there are 5 rows with 4 children in each row.

The centre of the third figure is empty. What digit should fit inside?

Solve the following series:
AZ, GT, MN, __, YB

I am green and found in the forest and have needles instead of leaves. What am I?
Hint 1: It can be used for Christmas decorations.
Hint 2: I have a strong, scent that is used in air fresheners.

A man desired to get into his work building, however he had forgotten his code.
However, he did recollect five pieces of information
* Fifth number + Third number = 14
* The fourth number is one more than the second number.
* The first number is one less than twice the second number.
* The second number and the third number equals 10.
* The sum of all five numbers is 30.

What is the code ?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

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?

Alpha is Beta's sister.

Gamma is a Beta mother.

Delta is Gamma's father.

Tango is Delta's mother.

Then,

How is Alpha related to Delta?