What we’re going

to do in this video are some real quick tests to see

if these three random numbers are divisible by any

of these numbers here. And I’m not going to focus a

lot on the why of why they’re divisible– we’ll do that in

other videos– but really just to give you a sense

of how do you actually test to see if this is

divisible by 2 or 5 or 9 or 10. So let’s get started. So to test whether any of

these are divisible by 2, you really just have to

look at the ones place and see if the ones

place is divisible by 2. And right over here,

8 is divisible by 2, so this thing is going

to be divisible by 2. 0 is considered to

be divisible by 2, so this is going to

be divisible by 2. Another way to think

about it is if you have an even number

over here– and 0 is considered to be

an even number– then you’re going to

be divisible by 2. And over here, you do not have

a number that is divisible by 2. This is not an even

number, this 5, so this is not divisible by 2. So I won’t write any 2 there. So we’ve gone through the 2s. Now, let’s work through the 3s. So to figure out if

you’re divisible by 3, you really just have to

add up all the digits and figure out if the

sum is divisible by 3. So let’s do that. So if I do 2 plus 7 plus 9

plus 9 plus 5 plus 8 plus 8, what’s this going

to be equal to? 2 plus 7 is 9. 9 plus 9 is 18, plus 9 is 27,

plus 5 is 32, plus 8 is 40, plus 8 is 48. And 48 is divisible by 3. But in case you’re not sure–

so this is equal to 48– in case you’re not sure whether

it’s divisible by 3, you can just add

these digits up again. So 4 plus 8 is equal to 12, and

12 clearly is divisible by 3. And if you’re not

even sure there, you could add those

two digits up. 1 plus 2 is equal to 3, and

so this is divisible by 3. This right over here,

let’s add up the digits. And we can do this one in

our head pretty easily. 5 plus 6 is 11. 11 plus 7 is 18. 18 plus 0 is 18. And if you want to add the 1

plus 8 on the 18, you get 9. So the digits add up to 9. So these add up to 9. Well, they add to 18, which

is clearly divisible by 3 and by 9, and these two

things will add to 9. So the important

thing to know is when you add up all the digits,

the sum is divisible by 3. So this is divisible by 3

as well, divisible by 3. And then finally, Let’s

add up these digits. 1 plus 0 plus 0 plus 7 is 8,

plus 6 is 14, plus 5 is 19. So we summed up the digits. 19 is not divisible by 3. So this one, we’re not going

to write a 3 right over there. It’s not divisible by 3. Let’s try 4. And to think about

4, you just have to look at the last

two digits and to see– are the last two

digits divisible? Are the last two

digits divisible by 4? Immediately, you can look

at this one right over here, see it’s an odd number. If it’s not going to

be divisible by 2, it’s definitely not going

to be divisible by 4. So this one’s not divisible by

any of the first few numbers right over here. But let’s think about one, 88. Is that divisible by 4? And you can do

that in your head. That’s 4 times 22. So this is divisible by 4. Now, let’s see. 4 goes into 60 15 times. And then to go from 60 to 70,

you have to get another 10, which is not divisible by 4. So that’s not divisible by 4. And you can even try to

divide it out yourself. 4 goes into 70,

let’s see, one time. You subtract, you get a 30. 4 goes into 30 seven times. You multiply, then you subtract. You get a 2 right over

here as your remainder, so it is not divisible by 4. Now, let’s move on to 5. Now, you’re probably already

very familiar with this. If your final digit is a 5 or

a 0, you are divisible by 5. So this one is not

divisible by 5. This one is divisible by 5. You have a 0 there, so

this is divisible by 5. And this, you have a

5 as your ones digit. So once again– finally– this

is divisible by something. It’s divisible by 5. Now, the number 6. The simple way to think

about divisibility by 6 is that you have to be

divisible by both 2 and 3 in order to be divisible by 6,

because the prime factorization of 6 is 2 times 3. So here, we’re

divisible by 2 and 3, so we’re going to be

divisible by– let me do that in a new

color– so we’re going to be divisible by 6. Here, we’re

divisible by 2 and 3, so we’re going to

be divisible by 6. And if you were just divisible

by 2 or 3, just one of them, then you wouldn’t

be able to do this. You have to have

both a 2 and a 3, divisibility by both of them. And here, you’re divisible

by neither 2 nor 3, so you’re not going

to be divisible by 6. Now, let’s do the test for 9. The test for 9 is very

similar to the test for 3. Sum up all the digits. If that sum is divisible

by 9, then you’re there. Well, we already summed

up the digits here, 48. 48 actually is not

divisible by 9. If you’re not sure, you can

add up the digits there. You get 12. 12 is definitely

not divisible by 9. So this thing right over

here is not divisible by 9. And this one over here, if

you added up all the digits, we got 18, which is divisible. It is divisible by 9. And I’m running out of colors. So this one is divisible by 9. All the digits added up to 18. And this one over here, you

don’t even have to add them up, because we already know

it’s not divisible by 3. If it’s not divisible by 3,

it can’t be divisible by 9. But if you did

add up the digits, you get 19, which is

not divisible by 9. So this also is

not divisible by 9. And then finally,

divisibility by 10. And this is the easiest one

of all, because you just have to see if you have

a 0 in the ones place. You clearly do not have a

0 in the ones place here. You do have a 0 in

the ones place there, so you are divisible by 10 here. And then finally, you don’t

have a 0 in the ones place here, so you’re not going

to be divisible by 10. Another way you

could think about it, you have to be divisible by both

2 and 5 to be divisible by 10. Here, you are divisible

by 5 but not by 2. But obviously,

the easiest one is to just see if you have

a 0 in the ones place.

from the bottom of my heart…THANK YOU..25 years ago when there were no you tube..if i dont undersatand a topic about math i have to walk 5 kilometers to my aunt who is a math teacher for her to explain it to me…now if my son having a problem about math i just click khan academy..from philippines thank you again

7 and 8 where is it

Hai

how did you get 4ร22

Thanks it helps

Nice video

Moimoimoimoimoimoi

very helpful ๐๐๐

FINALLY I GOT IT

Bad boy

Thanks din't understand until I watch this video cause my school is on of the best so it's hard.

thanks a lot ๐๐

nice educational video

Thank u๐

this really helped !

omg u made it so ez for me thx

thank you so much

thank you you helped i me

Your my tutor,YouTube…..

Thank You

Who needs human tutors

when ya got wifi right?

human tutors are expensive

Where was this in school. ๐

thank you for this video, this video help me a lot!!!

very very helpful thank you very much

Expalantion is so clear. Thanks!

nicely explained

Very good video I cannot subscribe I am very sorry

This helped alot thx so much

This helped alot thx so much

This helped alot thx so much

MATHS MADE MY LIFE SICK

This really helped๐๐๐๐๐๐๐๐ผ๐๐ผ๐๐ผ๐๐ผ๐๐ผ๐๐ผ

Thank you SO MUCH I have a test on Wednesday and it is Monday I was not here to learn it in class and my teacher won't repeat it in class so you are the best luv u

Boo

THAAAAAAAAAAANNNNKKKK YOOOOUUUU

Thank you so much

Thanks ei Michael keep รP the Greta Wรตro i got ja A on homeeriliselt

Oops wrong language lol

im using this as resurch for class

I do this in class it confuses me but this helpssss!!!

Math is my worst enemy. They call it the "Easiest Subject" But it is NOT. I am the worst in math and I hate it so much. If we discuss it, I will pretend to be listening. Why does Math even exist? Of Course all of us needs math but why do they have to teach us the complicated stuff. Math could be a lot easier if our teachers wouldn't have to teach us the complicated matters. Do you even know how hard it is to memorise (or whatever that spelling is) a whole notebook? Shame on teachers. >_<

thanks

This really work! ๐

thanks for the math videoโบ

thanks for the math videoโบ

Thank you so much this video is so helpful

2:46 7+6+5=18

Thank you soooo much ๐

I cant find out if 50 is divisible by 2,3,5,6, and 9 !!!!!!

thanks

Mental

Abuse

To

Humans

thank you for everything my school is a fan of khan academy

58129745812974 is divisible by 4 but 74 is not divisible by 4. Hows that possible?

This is awesome thanks Sal

๐ป ๐ฒ it is my life

this helped me alot i got an a

Thank you. ๐ I gotta A on my test today

THANK U

This skill is ganna make my head explode! ;-;

Man cane a dome try

Great video

If I could like a million times I would

if you are not sure at 03 , you can add them up too .

Very bad

Bakwas

@Marnier option nicr

Kyvd

thank you

I'm a highschool students, and yes! My teacher wants to recite divisibility 2,3,4,5,6,9,10.

How'd I get here?

Well I wish this is in the Philippines

Haha this is the thing I gotta do now๐ข it's sad. But thanks for the help!

when a human was tested by math

"oh no its the end of the world!"

because the test is hard and its just 1+1

Thanks so much for this video and other videos that Klan Academy has made because it help us a lot specially if u is confused or frustrated thanks so much again

THANK YOU AND I love all the videos Klan Academy ๐๐๐๐ฏ๐๐๐๐๐

I was absent so I didn't know what it meant but now you just helped me so much!

If it's not divisible by 3 it's not divisible by 8?! Lost me…

This video made me clarify all my doubts. Thanks!

Thanks khan academy. That was helpful!

thanks khan i need that!

Thanks this helped a lot lmao I have a test tomorrow on this and I did not study at aLl!1!

I hate math but this helped me

I hate math but this somehow helps

I want to like and dislike this vid ฯ times.

Real lifesaver

TY SOOOO MUCH KHAN!

I do this in math and I had no idea how to do it so I just doodle on my sheet of paper of IMPOSSSIBLENESS..

Thanks but i need help on my homework. It says "Odd number: A number

_divisible by ___.ู ูู ุนุฑุจู

i feel a little boring

I still don't get it ๐ฃ

helped alot

Nice

Thanks, really helped man

What about 7?

I want to know WHYYY! Not how. How can you understand if you don't know why?!

how about 7 and 8?

thank you, this was really helpful.

What is this used for exactly ?

Thank You So much!!!

i failed at my test I had a 0 out of 100

Wish me luck I have a test on this and more ahhh

you are so helpful. iโve been struggling on this for so long!

It's scary how he sounds and talks just like my math teacher…

Thx for the lesson tho.