What has no start, end, or centre?

Which tank will fill first?

People are waiting in line to board a 100-seat aeroplane. Steve is the first person in the line. He gets on the plane but suddenly can't remember what his seat number is, so he picks a seat at random. After that, each person who gets on the plane sits in their assigned seat if it's available, otherwise, they will choose an open seat at random to sit in. The flight is full and you are last in line. What is the probability that you get to sit in your assigned seat?

John went to meet his friend Jacob, but when he was about to reach the main gate, John notices that Jacob had a mighty dog who was fastened to the tree. The chain is long enough that it allows the dog to reach the main gate.

How can the John reach the main gate?

Count the number of squares in the picture below.

If EELS + MARK + BEST + WARY = EASY

What does HELP + BARK + WARD + LEAD equal?

Can you discover the missing number in this series?

37, 10, 82
29, 11, 47
96, 15, 87
42, ?, 15

Find the next number in the sequence

1, 2, 6, 21, 88, __?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

What makes this number unique: 8,549,176,320?