00:01
We have a collection of six shapes.
00:05
So we have two triangles, two circles, and two squares.
00:13
Okay, and some of them have a, some have b, some have c.
00:19
Now, we are going to be picking some of these shapes.
00:22
In part a, we pick three of them.
00:23
How many ways can we get three different shapes? so i can only assume these are not identical.
00:30
Maybe it's like this.
00:34
It doesn't matter too much.
00:35
But basically each shape has a label and a shape, and none of them are identical.
00:43
So we have six.
00:45
We are picking three of them.
00:47
The order doesn't really matter.
00:49
So that's combinations.
00:52
If the order doesn't matter, it's combinations.
00:54
If the order does matter, it's permutations.
00:57
The formula for combinations, n choose r, is n factorial over r factorial, n minus r.
01:05
So we need six factorial over three factorial, three factorial.
01:11
That will tell us how many ways to pick all of them...