You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

On a certain day, John celebrated his birthday. Two days later, his older twin brother Jacob celebrated his birthday.

Is this even possible? How can it be?

What 8 letter word can have a letter taken away and it still makes a word. Take another letter away and it still makes a word. Keep on doing that until you have one letter left. What is the word?

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?

In The 1st month of this year(the year 2013), I noticed that the date 13-1-13 (13 January 2013) is special.

This date is special as:

Date * Month = Year.

Can you figure out which year of this century has a maximum number of such dates?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see? What is it?

Can you find the six hidden animals in the picture below?

Find the number of squares in the below picture

Find the last number in the series below:

voN luJ yaM raM ---

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.