In an ordinary set of dominoes, there are 28 tiles. How many tiles would a set of dominoes contain if the values indicated on the tiles ranged not from 0 to 6, but from 0 to 12?

#
Try to understand why a standard set of dominoes has exactly 28 tiles.

## Solution

In such a set, there would be 13 "doubles." The number of other tiles is equal to the number of pairs from 13 numbers, which is $13 \cdot 12: 2$ = 78.

## Answer

91 tiles.