A number can be multiplied by multiple of nine
i.e 9 18 27 36 45 ...

and the resulting number consist of only one digit.

Can you identify the number ?

Can you replace the question mark with the correct number?

I am lying and I always lie. Tell me whether I am lying or telling the truth.

What has one letter and starts with an E?

In the image given, you can find several triangles. Can you count them all?

What do you think with the below Picture ?

What is the next number in the series?

15 29 56 108 208 ?

Two in a corner, one in a room, zero in a house, but one in a shelter. What am I?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

A new Engineering building containing 100 offices had just been completed. John was hired to paint the numbers 1 to 100 on the doors. How many times will John have to paint the number nine (9)?