Least Common Multiple (LCM)

[@DylRicho]

I prefer the terminology 'lowest common multiple' because "least common" can be misinterpreted as something entirely unrelated to the question at hand. With "lowest," you know that you're just looking for the smallest multiple that is found between all numbers in a given question.

[@girirajvardhan2722]

Can you explain with context?

[@Catimixto]

It's even worse in spanish, "Mínimo común multiplo"

[@travelvids9386]

​@girirajvardhan2722 least common can also mean rare.

[@fatimeh0]

hah ​@@obsyrd_freg

[@indrahx5905]

I came here to find out what "least common multiple" meant - because it isn't self explanatory. "Lowest common" makes way more sense and it's how we describe it in German as well (kleinstes gemeinsames Vielfaches).

[@davemaciver3681]

I'm planning to go back to uni in the next couple of years to study nursing which needs higher maths for some reason and I zoned out by that stage as I was already going to college for acting. I was GREAT at maths when I was in school, went to master classes and everything, but haven't bothered with it for 2 and a half decades. We're getting to the point of the course where I'm feeling proud of myself for getting stuff right! Thanks other Dave :)

[@albabahmed2735]

You are a blessing to us who forgot how to do basic math :D

[@suzi8364]

Me :3

[@user-ri7qy1en7l]

@@suzi8364 I forgot the multiplication table and now here I am starting from the very first

[@etherealbladerx8153]

You're "Checking Comprehension" music is as if the one who composed Earthbound music tried his hand at making the Wii shop channel music 😂 just a little funny to me 😊 great stuff as always

[@jayw8726]

I took me 20years to properly understand this since this was first explained in Grade 4 back in year 2000! Reckon my teacher was really lacking in her pedagogy! 😂

[@aliaoda8864]

Same

[@vdvoskin1]

there is an easier way to find the lest common multiple. lets take 18 and 24. start dividing both members by any common number that will yield a whole number, so first division is by 2: 18/2=9 and 24/2=12, remaining numbers can be further divided so we continue, second division is by 3: 9/3=3 12/3=4, we cannot divide anymore so we simply multiply the remaining numbers by the numbers we used to divide: 3*4*2*3=72.

[@sandpaper6095]

Genius

[@vaibhavgore165]

🙌

[@rizzwan-42069]

lemme try 12 and 80 divide by 4: 3 and 20. 20×3×4=12×20 clearly 240 this works and it's faster.

[@maithrisiri]

Thanks

[@emcmnd4196]

I figured out a incredibly fast way to find the least common multiple of two numbers. That is to find the ratio between the numbers and then simlify it into the simplest fraction form. Finally, multiple the small number of the two number with the big number of the fraction or the oppsite. The result is the least common multiple of the two numbers

[@NickHope]

By that method you can either multiply the numerator (the top number) of the simplified fraction by the denominator (the bottom number) of the original fraction, or vice versa with the same result.

[@zaini9715]

And how exactly would you find the simplest fraction? From a whole number??

[@ignacioleikis1784]

So the way to calculate the LCM of two numbers is to take the greatest number of factors of one number with the greatest number of factors from the other, irregardless of whether one factor repeats from one number to the other?

[@aashsyed1277]

yep. it's not told in other countries but it is told in india& pakistan

[@4karma860]

10% done with the playlist :3

[@Carrymejane]

HAHAHAHAHAHSAHAW

[@potat0wn3d]

16.5

[@asifshawon4511]

😂😂

[@tres-2buniverse729]

I think there is a simpler way to find the least common multiple by finding the biggest number which can divide both of the members,6 in this case 18/6=3 24/6=4 since 6 is common multiple for both numbers, then we multiply it with the result of the smallest numbers 3.4.6=72 (I dont know what Im doing though I suck at math so dont take this comment seriously)

[@tres-2buniverse729]

20/4=5 28/4=7 5.7.4=140 it worked for the second one too I think this works

[@tres-2buniverse729]

14/2=7 36/2=18 18.7.2=252 still works

[@tres-2buniverse729]

50/5=10 65/5=13 13.10.5=650 and this is the last still works too,I find it easier to multiply relatively bigger numbers compared to simplifying a big number

[@timurnachname1681]

What do you Think about the euclid Algorithm for LCM and HCF?

[@surjeetkumarsingh8251]

Timur nachname 2

[@yatu9002]

4:17 wait how is 4/12 bigger than 3/12 because when you divide you get 3 > 4 how it should be 4 > 3 or it is about how many times does the number fit into if the number fit's into it

[@shubhampal5328]

Dividing 4 into 12 parts will always be greater than diving 3 into 12 parts.

[@lutherjeremy6150]

hello, let me help yatu, imagine it's a circle piece of 4/12 and 3/12, if you simplify the 4/12 and 3/12, you get 1/3 and 1/4. Well, 1/3 circle is bigger than 1/4 circle right ? hope it helps🙏🏾

[@sultanmo9631]

Not me, a senior engineering student learning about LCM here :)

[@torosalvajebcn]

Another way to know which fraction is bigger is by cross multiplication

[@IzeDesu]

yes its easier but in some equations its more relevant to use LCM

[@AbhishekDwivedi-zx5nv]

Thank you Professor .

[@Zone_Ranger]

I like to use LCM(a,b)=a*b/GCD(a,b)

[@mayankarora5377]

what if the GCD of both numbers is 1 ? then this formula will imply LCM^2 which is obviously incorrect

[@Zone_Ranger]

@@mayankarora5377 then the lcm(a,b)=a*b

[@anthonystark6215]

Thank you, Professor!

[@Warlocktopus]

i thought LCM stood for lowest common multiple. I learned something ^^

[@ProfessorDaveExplains]

lowest = least, same thing!

[@topiado2073]

@@ProfessorDaveExplains 😄

[@ljr6490]

Isn't this kinda similar to an OR operator with the joining the most abundant primes?

[@sampannoi]

at first i thought he was a scary math techer but now i think i have to teach math to my school math scary teacher

[@lifewithtine2397]

Aight Xmas break to learn math 🔥

[@Metal_Icarus]

Thanks for making this video!

[@ShohsanamShonazarova]

Thank you, Professor.

[@lisaleidy344]

So helpful, thank you.

[@MemoUlloah]

Best channel ever!!

[@MiltosPol-qn3zh]

Very good

[@jonnyabatti5120]

In the comprehension 18 24, i factored 24 -> 12*2 and then 12 -> 4*3 and then 4 -> 2*2. Why am I wrong? Hope you can help me

[@asifbaig3811]

in order to find LCM we have to divide by lowest number because we have the lowest number 24/12= 2 and 18/9 = 2 so we won't be able to find least number. To find you have to 2 (24,18) 2(12,9) 2(6,3) 2(2,3) 3(1,3) (1,1) 2*2*2*2*3

[@asifbaig3811]

Please ignore the explanation is wring

[@zemo7483]

You have to write only primes as it factors. They are 24= 2*2*2*3 18=2*3*3 Now the 2 appears three times in 24's factors and, 3 appears twice in 18's factors so , LCM= 2*2*2*3*3 = 72

[@Lewis_8]

@@zemo7483 72 you mean...

[@zemo7483]

@@Lewis_8 yes

[@user-xf6zw5jy5v]

This helped allot

[@riiachka]

prof dave, i think that in the checking comprehendsion the answer for 18 and 20 is wrong. shouldnt it be 180?

[@ProfessorDaveExplains]

that's not one of the questions

[@riiachka]

@@ProfessorDaveExplains oh sorry i meant 24, not 20

[@jonnyabatti5120]

Joey Koch what i dont get is 24 if i factor it 12*2 and go from there i get the wrong answer. So when doing this what do i havw to keep in mind

[@jonnyabatti5120]

In the comprehension 18 24, i factored 24 -> 12*2 and then 12 -> 4*3 and then 4 -> 2*2. Why am I wrong?

[@0Coeus]

@@jonnyabatti5120 Nothing in your comment is wrong, you are just not done with all the steps. The prime factorisation of 24 is 2*2*2*3 (this is what you did) The prime factorisation of 18 is 2*3*3 To find the least common multiple you take the multiples of each whole number from the factorisation that has the most. 24 has three of the number 2, while 18 only has one, so we take the three. 18 has two of the 3's, while 24 only has one, so we take the two: 2*2*2*3*3 = 72 The video does not explain why this works, so I guess thats a story for another time :)

[@Brindleee]

Also this is soo helpful ❤

[@sphephilezwane5539]

You the best😭😭❤️❤️

[@yeayeah8321]

Thank you

[@tulsidevi6768]

Why unlikes for this video,🤔🤷

[@chourouk-gr9qg]

Thnx man

[@TaeKinzel]

I heard one fast food place made a 1/3 burger but people thought it was smaller so it didn't work out.

[@user-vh4jn4vv8e]

Nice

[@OwlbaTr0ss]

why does this work tho? I understad the process but I do not understand why it works, is it just one of those stupid "that's just the way it is in math things that just works and we don't know why"?

[@salah1x]

I understand it pretty well now, but I still don't find any useful application for it. I can find which fraction is greater simply by converting it to decimals instead of doing all of this

[@asdfcsa41fas]

works for small fractions. but it is highly unlikely that you are going to convert something like 57/960 into decimal. easier to find the lcm between 960 and whatever other number you are comparing it to.

[@sanjayx5394]

Lcm

[@hewathekoalafan7236]

Hi there can we get more

[@ProfessorDaveExplains]

Check my mathematics playlist, it has everything you need.

[@Brindleee]

Haha I love ur theme song

[@Sec0ndSqu4re]

GCD FOR GREATEST COMMON DENOMINATOR NOT LCM FRO LEAST COMMON MULTIPLE but at least its good

[@yodazo9658]

wow, I'm good at math

[@mamadwali4278]

❤❤❤

[@tysongordon4623]

who else is watching this for school this is how many people are l l v

[@rdw3721]

Me😂😂

[@therandomisedo7175]

6*9 huh 😂

[@MamathaPonugoti]

I not anshould last 4 questions

[@timppaUT]

No it doesn't!? :P You can't multiply infinity by three!? :D

[@popcorn_and_zero-coke_lady_fan]

6*9 240 😂

[@arunkulkarni5673]

1st

[@PrometheusDev-b6b]

Thanks Professor Dave.

[@yotubewatcher2497]

Thank you