Answer:
The probability that Alex ends up on the same team with at least one of his two best friends = 0.7222
Step-by-step explanation:
Number of ways to select r items from n, nCr = n!/(r! x (n-r)!)
P(Alex ends up on the same team with at least one of his two best friends) = 1 - P(Alex ends upon a team with none of his two best friends)
= 1 - P(4 other people in Alex's group are chosen from the 7 other kids)
= 1 - Number of ways to pick 4 kids from 7 / Number of ways to pick 4 kids from 9
= 1 - 7C4 / 9C4 = 1 - 35/126
= 0.7222
