If eleven plus two equals one, what does nine plus five equal?

Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1

What is represented by this rebus?

once
time

With the following rules:

(A) White can make up to 10 legitimate moves until all kings are checkmate.
(B) White can take any black piece except the king.
(C) The White King cannot be in check position at any time of the game.

Can you checkmate all kings in less than 10 moves?

The sum of a mother, her baby and her dog's weight is 170 Kg. How much does the baby weigh if the mother weighs 100 kg more than the combined weight of the baby and the dog, and the dog weighs 60 per cent less than the baby?

A man is found hanging dead from the ceiling of a room. The room’s dimensions are 15 x 15 x 15. The man is only 6ft tall and the rope was only 2ft long. There are no windows and only one door to the room. The door is bolted shut from the inside, and a puddle of water is under the man. How did he kill himself?

What can you hold in your right hand, but never in your left hand?

The following "Brain Bat" means Slow Down.
S
L
O
W

Using the same logic, can you tell us what does the following Brain Bat means ?
E
V
I
G

A shopkeeper allows people to buy a cold drink bottle in exchange for five empty bottles. A guy had a party at home and spent 77 cold drink bottles at the party. Now he has 77 empty bottles with him.

How many bottles do you think he can buy in exchange for those 77 empty bottles?

A detective visits his friend John just to discover that John's neighbour Dr Jacob was murdered. Dr Jacob, who is a mathematician wrote the murderer's name in a code word "Hcqtfz". There were five suspects
1. Ajit
2. Pankaj
3. Ganpat
4. Deenu
5. Hariya

The Detective was instantly able to find the murderer.
Can you?