9000148905

SubArea: 
Combinatorics
Level: 
A
Project ID: 
9000148905
Accepted: 
1
Clonable: 
0
Easy: 
1
The king has eight daughters. A dragon asks two daughters, otherwise he will destroy the whole country. In how many ways can we choose a pair of king's daughters for the dragon?
8!2!6!=28
8⋅7=56
82=64
8+7=15