How many people must be gathered together in a room, before you can be certain that there is a greater than 50/50 chance that at least two of them have the same birthday?

Two boys were admitted to a school. When the headmaster asks them about their parents, they tell him that they have same parents (father and mother). On further inquiry, it turns out that they both share the same date for their birthday.

"Are you twins," ask the headmaster.
"No," replies the boys.

Is it possible?

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

As shown in the image, the nine Dogs are square fenced. By constructing just two square fences can you make sure that two Dogs cannot meet each other without crossing the fence?

I purchased an awesome ice cream cone having 5 different flavour scoops.
Five flavours are pistachio, mint-chip, strawberry, marshmallow, and raspberry

I will give u some clues so that you can figure out the order of flavours from bottom to top.
1. The bottom flavour of the cone has 10 letters.
2. The marshmallow scoop is between the pistachio and the mint-chip scoop.
3. marshmallow is the raspberry scoop but below the mint-chip scoop.

So can you figure out the flavour of ice cream in order from bottom to top?

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 king sentenced a man to the death sentence for some crime he had committed. Known for his kindness, the king told the culprit that he had a choice to die in a way he decides.

The culprit was clever and said something that saved him from death. What method do you think he must have chosen for his death?

I am Huge on Sunday and Saturday.
I am small from Tuesday to Thursday.
I do not exist on Monday and Friday.
Who am I?

Three doctors said that Bill was their brother. Bill says he has no brothers. How many brothers does Bill actually have?