Which is Odd One Out and why?

4377

3954

9862

8454

9831

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.

Which Number is the odd one out?

A) 7145
B) 2716
C) 5321
D) 4135

You are given with the following sum. Each of the letters can be decoded as a digit. If we tell you that D = 5, then can you solve it entirely?

DONALD
+GERALD
=ROBERT

Replace the letters of words with a number so that the below equation holds true

BASE +
BALL
---------
GAMES
----------

Replace the question mark with the correct number.

2 + 2= 4
3 + 3= 18
4 + 4= 48
5 + 5= ?

Can you find out what is missing?

1 3 5
2 4 ?

Hint: It's not six. Think out of the box.

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

Solve the equation by replacing the alphabet with numbers.

MOM + MOM + NO = BOOK=

A man embarked on a questionnaire game. He kept asking the same question to whomever he found. The answer each time was different.

Can you guess what the question was?