Why is the Hole below a Lock?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

The answer I give is yes, but what I mean is no. What was the question?

I know a 5-digit number having a property that With a 1 after it, it is three times as large as it would be with a one before it.

Guess the number?

If I put in one bird per cage, I have one bird too many. If I put in two bird per cage, I have one cage too many. How many cages and birds do I have?

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

How can you drop a raw egg from a height onto a concrete floor without cracking it?

You stand in front of two doors. A guard stands next to each door. You know the following things: one path leads to paradise, the other leads to death. You cannot distinguish between the two doors. You also know that one of the two guards always tells the truth and the other always lies. You have permission to ask one guard one question to discover which door leads to paradise. What one question would you ask to guarantee you enter the door to paradise?

In the image below, can you find the value of an angle(y)