请教PERP数学2道 多谢

secretnancy

26. 3282-!-item-!-187;#058&003293
There are 10 children in a company's day-care center, and a pair of children is to be selected to play a game.  At most, how many different pairs are possible?
(A) 100
(B) 90
(C) 50
(D) 45
(E) 25
27. 3330-!-item-!-187;#058&003295
38, 69, 22, 73, 31, 47, 13, 82
Which of the following numbers is greater than three-fourths of the numbers but less than one-fourth of the numbers in the list above?
(A) 56
(B) 68
(C) 69
(D) 71
(E) 73

哈哈柚

第一题，10个孩子任意选2个做游戏，那么组合就是C10 2=10！/8!2!=45
第二题，将这8个数字从小到大排列，13 22 31 38 47 69 73 82，问大于3/4但小于1/4的数，一共有8个数，那就是问大于6个数但小于2个数的数，也就是69至73中的数，71

secretnancy

谢谢