math
posted by Katie on .
Mr. and Mrs. Smith each bought 10 raffle tickets. Each of their three children bought four tickets. If
4280 tickets were sold in all, what is the probability that the grand prize winner is:
a. Mr. or Mrs. Smith? b. one of the 5 Smiths? c. none of the Smiths?

a) The probability for one or the other is 10/4280 (1/428). For one of the two, add each of their probabilities (1/428)+(1/428) gives an answer of 1/214.
b) The probability for any one child is 4/4280 (1/1070). Adding together the three children's probability (1/1070)+(1/1070)+(1/1070) gives an answer of 3/1070.
c)Since the total tickets for the Smiths are 32 tickets, 428032 (4248) tickets are possessed by others. 4248/4280 (531/535) is the probability another will win. 
a. 10/4280
0.0023
b. (10+12) = total tickets
22/4280 = 0.051
c. (428022) divided by 4280
0.9949