How many words can a pen with half refill write?

Whats the next number in the below number sequence pattern.

How many people must be gathered together in a room, before you can be certain that there is a greater than 50/50 chance that at least two of them have the same birthday?

There are nine letters in the below-given diagram. You have to form a nine-letter word using these letters.

You have two strings whose only known property is that when you light one end of either string it takes exactly one hour to burn. The rate at which the strings will burn is completely random and each string is different.

How do you measure 45 minutes?

A network of 20 x 10 squares is given to you.

Can you calculate how many unique squares and rectangles can be formed combining two or more individual squares ?

What's a single-digit number with no value?

By using 'because' continuously three times, can you make an English statement ?

I have Rs.50 and I spend it in the way as below.

What is a word made up of 4 letters, yet is also made up of 3. Sometimes is written with 9 letters, and then with 4. Rarely consists of 6, and never is written with 5.