00:01
Alright, for this problem, we're supposed to determine whether these numbers are divisible by 3, 6, and or 9.
00:13
Now, for all of these, what you do is you add the digits in the number.
00:20
And if that number is divisible by 3, then the number is divisible by 3.
00:27
If it's divisible by 3 and it's an even number, in other words, divisible by 2 and 3 both, it's divisible by 6.
00:36
And if you add the digits and that sum is divisible by 9, then the whole number is divisible by 9.
00:43
So, let's look at the first one.
00:47
I've got 1 plus 1 is 2 plus 2 is 4.
00:52
Here's what i'm doing.
00:53
1 plus 1 plus 2 plus 8.
00:57
So, 1 plus 1 is 2 plus 2 is 4 plus 8 is 12.
01:02
Alright, so i get 12 when i add these.
01:06
12 is divisible by 3 and it's even, so it's divisible by 6.
01:13
12 is not divisible by 9, so this number is not divisible by 9.
01:18
Okay, so for here, i've got 2 plus 1 is 3 plus 1 more is 4.
01:26
So, that's none of them.
01:29
Here, i've got 2 plus 2 is 4 plus 3 is 7 plus 5 is 12 again.
01:36
And it's odd, so that's just divisible by 3.
01:41
Here, i've got 3 plus 1 is 4, 5, 6, 7, 8.
01:45
So, that's none.
01:49
Here, i've got 3 fours is 12 plus 5 is 17.
01:54
So, that's none.
01:57
Here, i've got 8 plus 8 is 16, 17, 18.
02:02
So, it's divisible by 3.
02:05
It's even, so it's divisible by 6.
02:08
And 18 is also divisible by 9.
02:11
So, that one's divisible by all three of them.
02:16
For this number, i've got 5 plus 2 is 7 plus 2 is 9 plus 8 is 17.
02:23
So, that's none.
02:24
Here, i've got 5 and 4 is 9.
02:28
So, it's divisible by 3.
02:30
It's even, so it's divisible by 6 also...