7.2. A pair of dice is tossed. (See Example 7.2.) Find the number of elements in each event: (a) A = {two numbers are equal} (c) C = (5 appears on the first die} (b) B = {sum is 10 or more} (d) D = (5 appears on at least one die} Use Fig. 7-1(b) to help count the number of elements in the event. (a) A = ( (1, 1). (2, 2). .... (6, 6)], so m(A) = 6. (b) B = [(6, 4). (5,5). (4, 6). (6, 5), (5, 6), (6, 6) ], son( B) = 6. (c) C = ((5, 1). (5, 2). .... (5, 6)]. son(C) = 6. (d) There are six pairs with 5 as the first element, and six pairs with 5 as the second element. However, (5, 5) appears in both places. Hence "(D) =6+6-1 = 11 Alternately, count the pairs in Fig. 7-1(b) which are in D to get n (D) = 11