word problem

Question

The smallest set of dominos uses only the numbers 0 to 6.Each domino has two numbers on its face,and once a combination of numbers is used,it is not repeated.How many dominos are in the smallest set of dominos?

Answer 1

There are seven dominos where the least number is 0

there are six dominos where the least number is 1

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there is one domino where the least number is six.

 

7 + 6 + 5 + 4 + 3 + 2 + 1 = 28