What is full of holes but still holds water?

Can you find the odd number in the following?

2716, 4135, 5321 and 7145

In a competitive exam, each correct answer could win you 10 points and each wrong answer could lose you 5 points. You sat in the exam and answered all the 20 questions, which were given in the exam.
When you checked the result, you scored 125 marks on the test.

Can you calculate how many answers given by you were wrong?

You walk into an old horror house. It has no power or plumbing. Once inside, you see three doors. Each door has a number on it. Behind each door is a way for you to die. Behind door number one, you die by getting eaten by a lion. Behind door number two, you die by getting murdered. Behind door number three, you die by an electric chair. You can’t turn back, so you have to go through a door. Which door do you go through?

Once upon a time, there was a bus conductor who was extremely rude to all the passengers. On a certain day, a young and charming lady tried boarding the bus. But he did not stop the bus. As a result, the girl came under the bus and was killed. The agitated passengers took the conductor to the police station. The police took him to the court for trial. In the court, the judge gave him death sentence.

He is then taken to the electrocution chamber. In that room, there is a chair in the center of the room and a banana peel lies just behind the chair. The conductor is strapped to that chair and is being exposed to a high voltage current. But to everyone�s surprise, he is able to survive through the current that is enough to kill two people at once. The judge decides that it is a miracle and sets the conductor free.

The conductor then returns back to his profession. After a few months, a middle aged lady tries to board the bus. The conductor does not stop the bus and as a result the lady gets run over by the bus which kills her on the spot. The agitated passengers take him to the police. The police takes him to the court for the trial. In the court, the judge decides for capital punishment for the conductor.

The conductor is taken to the electrocution chamber again. In that chamber, there is a chair in the middle of the room and a banana peel lies behind the chair. He is strapped to the chair and exposed to a high voltage. To everyone�s surprise, he survives again. Thus, the judge sets him free.

The conductor returns back to his profession. After a few months. An old lady tries to board the bus. The bus conductor after remembering his previous actions, stops the bus. But unfortunately, the old lady slips while climbing up the bus and dies due to his injuries. The passengers take him to the police again. The police takes him back to the court. Though the judge knows that he is not guilty, he sentences him to death knowing his previous record.

The conductor is taken to the electrocution chamber again. He is strapped to the chair in the center of the room behind which, there is a banana peel. He is exposed to the current and this time he is killed instantly.

Why did he die this time and not the previous times?

A doctor and a boy were fishing. The boy was the doctor’s son, but the doctor was not the boy’s father. Who was the doctor?

The first person saw the bridge step on it and crossed,
the second person saw the bridge did not step on it but crossed,
the third person did not see the bridge did not step on it but crossed.
Who are these people?

There is a box full of marbles,
all but two are blue,
all but two are green,
and all but two are red.

How many marbles are in the box?

As a whole I am both
safe and secure.

Behead me and I become
a place of meeting.

Behead me again and I am
the partner of ready.

Restore me, and I become
the domain of beasts.

What am I?

15 caves are arranged in a circle at the temple of doom. One of these caves has the treasure of gems and wealth. Each day the treasure keepers can move the treasure to an adjacent cave or can keep it in the same cave. Every day two treasure seekers visit the place and have enough time to enter any two caves of their choice.

How do the treasure seekers ensure that they find the treasure in the minimum number of possible days?