42. In a regular set of dominoes, there are 28 tiles. How many tiles would a domino set have if the values indicated on the tiles ranged not from 0 to 6, but from 0 to $12?$
42. If the values on the dominoes changed from 0 to 12, then the dominoes would be:

![](https://cdn.mathpix.com/cropped/2024_05_21_00604dc020e3721fc1f4g-127.jpg?height=277&width=831&top_left_y=844&top_left_x=630)

This means there would be 13 dominoes with zero, 12 dominoes with one (but without zero), 11 dominoes with two (but without zero and one), and so on. Therefore, the total number of dominoes would be:

$13+12+11+\ldots+3+2+1=(13+1) \cdot 6+7=91$.