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A blood bank needs 12 people to help with a blood drive. 19 people have volunteered. Find how many different groups of 12 can be formed from the 19 volunteers.
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A blood bank needs 1212 people to help with a blood drive. 1919 people have volunteered. Find how many different groups of 1212 can be formed from the 1919 volunteers.\newlineAnswer:

Full solution

Q. A blood bank needs 1212 people to help with a blood drive. 1919 people have volunteered. Find how many different groups of 1212 can be formed from the 1919 volunteers.\newlineAnswer:
  1. Identify Concept: Identify the mathematical concept needed to solve the problem.\newlineTo find the number of different groups of 1212 that can be formed from 1919 volunteers, we need to use the concept of combinations. The formula for combinations is C(n,k)=n!k!(nk)!C(n, k) = \frac{n!}{k!(n-k)!}, where nn is the total number of items, kk is the number of items to choose, and “!!” denotes factorial.
  2. Apply Formula: Apply the formula for combinations to the given numbers.\newlineWe have 1919 volunteers in total (n=19n = 19) and we want to form groups of 1212 (k=12k = 12). So we need to calculate C(19,12)=19!12!(1912)!C(19, 12) = \frac{19!}{12!(19-12)!}.
  3. Simplify Expression: Simplify the expression by calculating the factorials and the division. C(19,12)=19!12!×7!=19×18×17×16×15×14×137×6×5×4×3×2×1C(19, 12) = \frac{19!}{12! \times 7!} = \frac{19 \times 18 \times 17 \times 16 \times 15 \times 14 \times 13}{7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1} since the factorials from 11 to 1212 cancel out with part of the 19!19! factorial.
  4. Perform Calculations: Perform the calculations.\newlineC(19,12)=19×18×17×16×15×14×137×6×5×4×3×2×1=503885040=10C(19, 12) = \frac{19 \times 18 \times 17 \times 16 \times 15 \times 14 \times 13}{7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1} = \frac{50388}{5040} = 10

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