What's the only room from which no one can enter or leave

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?

When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

Three people check into a hotel. They pay $60 for the rent of the room. After they check-in, the manager realize that the rent for the room is $55. So, he gives $5 to the bellboy and asks him to give it to them. The bellboy thinks that it will be difficult for the three people to share $5 among them and seeking the personal benefit, he pockets $2 and gives the remaining $3 to them.

Now, each person paid $20 and got back $1. In this manner, each of them paid just $19 which totals to the amount of $57. The bellboy has $2 with him and adding them, we get $59. So where is the remaining $1?

Six glasses are in a row. The first three are filled with milk and the last three are empty. By moving only one glass, can you arrange them so that the full and the empty glasses alternate?

Using eight eights and addition only, can you make 1000?

The day before yesterday I was 25 and the next year I will be 28. This is true only one day in a year. What day is my birthday?

If one and a half boys, eat one and a half burgers in one and a half hours.

How many burgers can 9 boys eat in 3 hours?

Which of the following words don't belong in the group and why?
CORSET, COSTER, SECTOR, ESCORT, COURTS

Find the hidden tiger in the given optical illusion ?