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In a class of 66, there are 22 students who forgot their lunch. If the teacher chooses 22 students, what is the probability that both of them forgot their lunch?

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Q. In a class of 66, there are 22 students who forgot their lunch. If the teacher chooses 22 students, what is the probability that both of them forgot their lunch?
  1. Calculate Total Ways: Determine the total number of ways to choose 22 students from a class of 66.\newlineWe use the combination formula, which is C(n,k)=n!k!(nk)!C(n, k) = \frac{n!}{k!(n-k)!}, where nn is the total number of items, and kk is the number of items to choose.\newlineFor our case, n=6n = 6 and k=2k = 2.\newlineC(6,2)=6!2!(62)!=(6×5)(2×1)=15C(6, 2) = \frac{6!}{2!(6-2)!} = \frac{(6\times5)}{(2\times1)} = 15
  2. Choose Students with No Lunch: Determine the number of ways to choose 22 students who both forgot their lunch.\newlineSince there are 22 students who forgot their lunch, we need to choose 22 out of these 22.\newlineC(2,2)=2!(2!(22)!)=2!(2!0!)=11=1C(2, 2) = \frac{2!}{(2!(2-2)!)} = \frac{2!}{(2!*0!)} = \frac{1}{1} = 1
  3. Calculate Probability: Calculate the probability that both students chosen forgot their lunch.\newlineProbability = Number of favorable outcomes / Total number of outcomes\newlineProbability = C(2,2)C(6,2)=115\frac{C(2, 2)}{C(6, 2)} = \frac{1}{15}

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