When can we add 2 to 11 and get 1 as the correct answer?

Count the squares in the matchstick puzzle below?

What are the 50th, 63rd and 100th numbers in the sequence below?
4, 5, 8, 8, 9, 9, 12, 13, 13, 13, 17, 18, ...

You and your two friends are working in a multinational company. How can you three find out the average salary of you all without disclosing your own salary to the other two?

A professor thinks of two consecutive numbers between 1 and 10.
'A' knows the 1st number and 'B' knows the second number

A: I do not know your number.
B: Nor do I know your number.
A: Now I know.

What are the four solutions for this?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

A father's child, a mother's child, yet no one's son.

Who am I?

Why is the Hole below a Lock?

I am a ten letters word
The first four letters have the power to rule,
Next, four-letter can be eaten.
The next three-letter represents a lady.
I can fly as well

what am I looking for?

Can you quickly find which two matchstick figures are identical?