ecall from Example 1 that whenever Suzan sees a bag of marbles, she grabs a handful at random. She has seen a bag containing two red marbles, two green ones, three white ones, and two purple ones. She grabs seven of them. Find the probability of the following event, expressing it as a fraction in lowest terms. HINT [See Example 1.] She does not have all the red ones.
number of red marbles = 2
number of green marbles = 2
number of white marbles = 3
and number of purple marbles = 2
Hence n = total number of marbles in a bag = 2 + 2 + 3 + 2 = 9
k = number of marbles selected ( grabs) =7.
Hence without restriction total number of ways to choose 7 from 9 marbles =
Given condition the selected marbles does not contain any red marbles.
Remaining marble = total marbles - red marbles = 9-2 =7
Hence number of ways to choose 7 marbles ( without any red marbles) in ways.
P ( She does not have all the red ones) = .
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