I look at you, you look at me I raise my right, you raise your left. What am I?

Speaking of rivers, a man calls his dog from the opposite side of the river. The dog crosses the river without getting wet, and without using a bridge or boat. How?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

I am a word that begins with the letter “i.” If you add the letter “a” to me, I become a new word with a different meaning, but that sounds exactly the same. What word am I?

Jenifer and Jesica are having a conversation.

Jenifer: I am definitely not over 30.
Jesica: I am 28 and you are surely 5 years older to me at least.
Jenifer: No, you are at least 29.

You are told that both of them are lying throughout in the conversation. Can you find their respective ages?

Can you make the below equation true by using any three numbers from "1, 3, 5, 7, 9, 11, 13 and 15"?

( ) + ( ) + ( ) = 30

I never was there, I am always to be.
You have never ever seen me, not ever you will.
Yet I am the confidence of everyone.

Who Am I?

The person who makes it has no need for it; the person who buys it has no use for it. The person who uses it can neither see nor feel it. What is it?

Eight of us go fourth, not back, to protect our king from an attack. What are we?

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?