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Ms. April likes for the twenty students in her
class to have a carton of milk each day at break
time. She sends three of her students down to
the cafeteria to ask for the cartons of milk, but
she likes to mix things up a bit and wants to
send a different group of students down every
day. Will she have enough different groups of
three students in her class of twenty students to
send a different group every day of the school year? (There are 180 days in the school year)

Respuesta :

sqdancefan

9514 1404 393

Answer:

  yes

Step-by-step explanation:

There are 20 ways to choose the first student, 19 ways to choose the second student, and 18 ways to choose the third student. Chosen this way, the same three students can be chosen 3×2×1 = 6 different ways. So, the number of different choices of 3 students will be ...

  (20×19×18)/(3×2×1) = 1,140

There are easily enough different combinations of 3 students to have a different combination each day.

_____

Additional comment

The number found above is the number of combinations of 20 students taken 3 at a time: 20C3 or C(20, 3). The value can be computed from ...

  nCk = n!/(k!(n-k)!)

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