How many spots are there on a standard domino set?

Question

There are several books on a bookshelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

Answer 1

Double-six and double-nine are the most commonly used sets of dominoes.
It is possible to determine the number of spots in a domino set of any size by using the formula (n+1)(n+2) / 2, where n equals the largest value available in the set. The spots on a domino set are also sometimes known as dots or pips.
6x6 has 28 tiles and 168 pips.
9x9 has 55 tiles and 495 pips.