I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

A new Engineering building containing 100 offices had just been completed. John was hired to paint the numbers 1 to 100 on the doors. How many times will John have to paint the number nine (9)?

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?

Forwards I am heavy, backward I am not. What am I?

Keyboard words are not in alphabetical order, Why?

13 decks of cards have been mixed. What is the minimum number of cards that must be taken out from the above-mixed cards to guarantee at least one 'four of a kind?

As shown in the picture below, we can see a boy hanging on the tree branch to save his life. There are various ways in which he can die like1. A snake hanging toward the right waiting to bite the boy.2. A roaring Lion near the tree.3. Two crocodiles are ready to attack if the boy reaches near water. The tree is chopped to some extent, so can fall as if he moves a lot. Can you give this boy an escape plan?

The centre of the third figure is empty. What digit should fit inside?

Find the last number in the series below:

voN luJ yaM raM ---

You order chicken wings at KFC in the boxes of 6, 9 and 20. What is the largest number of wings that you cannot obtain by buying in any combination of the boxes?