Question

How to do this question plz answer ​

Answer 1

9514 1404 393

Answer:

  300

Step-by-step explanation:

There are 25 ways to select the first student. After that student is removed from the selection pool for the second student, there are 24 ways to select the second student. This gives 25·24 = 600 ways to select 2 students in a particular order.

Since we don't care about the order, we can divide this number by the number of ways two students can be ordered: AB or BA, 2 ways.

  600/2 = 300

There are 300 ways to pick a combination of two students from 25.

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Additional comments

This sort of selection (2 out of 25) has a formula for it, and an abbreviation for the formula.

 "n choose k" can be written nCk or C(n, k)

The function is a ratio of factorials:

  nCk = n!/(k!(n-k)!)

If you can typeset this, it is written ...

  $\displaystyle\binom{n}{k}=\frac{n!}{k!\cdot(n-k)!}$

This is different from the formula for the number of permutations of n things taken k at a time. That would be written nPk or P(n, k) = n!/(n-k)!.

Answer 2

Answer:

300

Step-by-step explanation:

600 / 2 = 300