Question

Suppose that 22 ​thank-you notes are written and 22 envelopes are addressed.​ accidentally, the notes are randomly inserted into the envelopes and mailed without checking the addresses. what is the probability that all the notes will be inserted into the correct​ envelopes?

Answer 1

$|\Omega|=22!=1,124,000,727,777,607,680,000\\ |A|=1\\\\ P(A)=\dfrac{1}{1,124,000,727,777,607,680,000}$