Solve this riddle by finding the odd one out from the rest.

Our product and our sum always give the same answer. Who are we?

We have four gears with below features=> Both Gear A and D has 60 teeth=> Gear B has 40 teeth=> Gear C has 20 teeth=> Every two minutes, Gear B makes 25 full turns.What is the relative speed of Gear A and Gear B?

If 1+9+8=1, what is 2+8+9?

I add 5 to 9 and get 2. The answer is correct, so what am I?

What number comes next in this sequence:
7 8 5 5 3 4 4 _

Can you make four (4) nines (9) equal 100?

How old is your son? asked a man to his neighbour. My son is five times as old as my daughter and my wife is five times as old as my son. I am twice as old as my wife whereas my grandmother, who is celebrating her eighty-first birthday is as old as all of us put together.

How old is the man's son ?

What three numbers, none of which is zero, give the same result whether they’re added or multiplied?

From a pack of 52 cards, I placed 4 cards on the table.

I will give you 4 clues about the cards:

Clue 1: Card on left cannot be greater than the card on the right.
Clue 2: Difference between the 1st card and 3rd card is 8.
Clue 3: There is no card of an ace.
Clue 4: There are no face cards (queen, king, jacks).
Clue 5: Difference between the 2nd card and 4th card is 7.

Identify four cards?