Có bao nhiêu cách sắp xếp 5 bạn học sinh A, B,C, D,E ngồi vào một chiếc ghế dài sao cho: a)C ngồi chính giữa
b)A và E ngồi ở 2 đầu ghế

Twelve less than a number is at most 20

Describe the symmetry of the figure. identify lines of symmetry, if any. find the angle and the order of any rotational symmetry.

Consider a bag that contains 220 coins of which 6 are rare indian pennies. for the given pair of events a and b, complete parts (a) and (b) below. a: when one of the 220 coins is randomly selected, it is one of the 6 indian pennies. b: when another one of the 220 coins is randomly selected (with replacement), it is also one of the 6 indian pennies. a. determine whether events a and b are independent or dependent. b. find p(a and b), the probability that events a and b both occur.