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A basketball team has 10 players. Before each game, the coach picks 2 of those players to carry the team's water jug.
How many different groups of 2 players can the coach pick?

A basketball team has 1010 players. Before each game, the coach picks 22 of those players to carry the team's water jug.\newlineHow many different groups of 22 players can the coach pick?

Full solution

Q. A basketball team has 1010 players. Before each game, the coach picks 22 of those players to carry the team's water jug.\newlineHow many different groups of 22 players can the coach pick?
  1. Define Combination Formula: To determine the number of different groups of 22 players that can be picked from 1010 players, we need to use the combination formula, which is defined as 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.\newlineIn this case, n=10n = 10 (total players) and k=2k = 2 (players to be picked).
  2. Calculate Factorial of nn: First, we calculate the factorial of nn, which is 10!10! (1010 factorial).\newline10!=10×9×8×7×6×5×4×3×2×110! = 10 \times 9 \times 8 \times 7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1
  3. Calculate Factorial of kk: Next, we calculate the factorial of kk, which is 2!2! (22 factorial).\newline2!=2×12! = 2 \times 1
  4. Calculate Factorial of (nk)(n - k): We also need to calculate the factorial of (nk)(n - k), which is (102)!(10 - 2)! or 8!8! (88 factorial).\newline8!=8×7×6×5×4×3×2×18! = 8 \times 7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1
  5. Apply Combination Formula: Now we can plug these values into the combination formula:\newlineC(10,2)=10!(2!(102)!)C(10, 2) = \frac{10!}{(2!(10 - 2)!)}\newlineC(10,2)=10!(2!×8!)C(10, 2) = \frac{10!}{(2! \times 8!)}
  6. Simplify Factorials: We simplify the factorials by canceling out the common terms in 10!10! and 8!8!:\newlineC(10,2)=10×9×8!2×1×8!C(10, 2) = \frac{10 \times 9 \times 8!}{2 \times 1 \times 8!}\newlineC(10,2)=10×92×1C(10, 2) = \frac{10 \times 9}{2 \times 1}
  7. Find Number of Combinations: Perform the division and multiplication to find the number of combinations:\newlineC(10,2)=10×92C(10, 2) = \frac{10 \times 9}{2}\newlineC(10,2)=902C(10, 2) = \frac{90}{2}\newlineC(10,2)=45C(10, 2) = 45

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