# Math Help - Permutations.. a quick question

1. ## Permutations.. a quick question

How exactly do i go about solving these questions:an example would be fine

2. Example: $
\frac{{n!}}{{\left( {n - 1} \right)!}} = \frac{{n\left( {n - 1} \right)!}}{{\left( {n - 1} \right)!}} = n
$

3. you dont have to use one of my questions but can u do an example with numbers? id understand more

4. Just replace n by a number to see an example, e.g. n = 5:

$\frac{{5!}}{{4!}} = \frac{{5 \cdot 4!}}{{4!}} = 5$

5. thanks... im having trouble with this one too.. funny how i get all the hard questions but not these anyways no solving needed here just an example will do( my book sucks)

6. The first one is exactly 5!, no?

Let's take a look at the second one. It starts like 8!, but that is 8*7*6*5*4*3*2*1. But the last part 5*4*3*2*1 isn't there, and that's exactly 5!. So we need 8!, but not the 5!, so 8!/5!. Check:

$
\frac{{8!}}{{5!}} = \frac{{8 \cdot 7 \cdot 6 \cdot 5!}}{{5!}} = 8 \cdot 7 \cdot 6
$

7. so say it was 30*29 whats the answer?

8. Try the same approach as above.