A fair coin is flipped twelve times. What is the probability of the coin landing tails up exactly nine times?

Step-by-step explanation:

Given that a fair coin is flipped twelve times.

It means the number of possible sequences of heads and tails would be:

2¹² = 4096

We can determine the number of ways that such a sequence could contain exactly 9 tails is the number of ways of choosing 9 out of 12, using the formula

Plug in n = 12 and r = 9

                   ∵

                          ∵

Thus, the probability will be:

Thus, the probability of the coin landing tails up exactly nine times will be:

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step-by-step explanation: