What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

If we tell you that there is a relation between the numbers and letters in the given figure, can you analyze it and find the missing letter in the last box?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

What has 88 keys?

Using four sevens (7) and a one (1) create the number 100. Except for the five numerals, you can use the usual mathematical operations (+, -, x, :), root and brackets ()

John named his first son Alpha, second Beta, third Charlie and fourth Delta. What is the fifth son's name?

It has a long neck, A name of a bird, Feeds on cargo of ships, It's not alive,

What is it?

A man dies of old age on his 25 birthday. How is this possible?

Can you discover the missing number in this series?

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

Can you place three balls such that the equation shown in the picture holds true?