7. Right triangle PQR is to be constructed in the xy-plane so that the right angle is at P and PR is parrallel to the x-axis. The x-and y-coordinates of P,Q,and Rare to be integers that satisfy the inequalities -4<=x<=5,6<=y<=16,how many different triangles with these properties could be constructed? (A) 110 (B) 1100 (C) 9900 (D) 10000 (E) 12100
8. A box contains 100 balls, numbered from 1 to 100. If three balls are 0selected at random and with replacement from the box,what is the probability that the sum of the three numbers on the balls 0selected from the box will be odd? (A) 1/4 (B) 3/8 (C) 1/2 (D) 5/8 (E) 3/4
9. (0-9) 要组成三位电话号码,第一位不能是0或1,三位数中相邻两位不能为同一数. (e.g. 227 not acceptable, but 272 acceptable),求可以组成多少个这样的电话号码?