Question

Question from sis

What is the least common multiple of
18 and 40?
A. 2
B. 40
C. 180
D. 360

Answer 1

i'm not allowed to answer for my sis

Answer 2

To find the LCM, first factor the 2 numbers. Then find the product of all the factors they share and all the factors that are not shared.

Answer 3

So 18 = 3*3*2
40 = 5*2*2*2

Answer 4

So the only one they share is one of the 2's.

Answer 5

or
18*1=18 14*1=14
18*2=36 14*2=28
18*3=54 14*3=42
18*4=74 14*4=56
18*5=90 14*5=70
18*6=108 14*6=84
18*7=126 14*7=98
18*8=146 14*8=112
18*9=162 14*9=126
so this can get pretty long
but we see that the lcm(18,14)=126

Answer 6

that's a complicated way to find it.

Answer 7

lol and really long way sometimes

Answer 8

The LCM is 5*3*3*2*2*2

Answer 9

oh 40 darn

Answer 10

The LCM of any set of numbers l and k is the product of A and B where A is the product of all the factors l and k have in common, and B is the product of all the factors l and k do not share.

Answer 11

1*40=40
2*40=80
3*40=120
4*40=160
5*40=200
6*40=240
7*40=280
8*40=320
9*40=360
so yes the lcm(18,40)=360 doing it the long way lol

Answer 12

thanks and that is way long

Answer 13

you do really big numbers you might want to make a computer mathematical algorithm lol

Answer 14

I would us the fact that LCM(x,y)=x*y/GCD(x,y)

Answer 15

if you choose to do the long way that is
polpak's way is much better

Answer 16

thats nice zarkon

Answer 17

use the euclidean algorithm to find the GCD

Answer 18

XD

Answer 19

Usually my way is faster than euclid's for the kinds of LCM's they have you look for in this level of math ;p

Answer 20

40=18*2+4
18=4*4+2
4=2*2
-------------------------
gcd is 2

Answer 21

sure...but for large numbers it could be hard to factor the number into primes

Answer 22

Yep

Answer 23

or looking at this we only see that they have 2 in common
\[40=2*2*5, 18=2*3*3\]

Answer 24

oops 40=2*2*2*5

Answer 25

so using zarkon's formula we get
lcm(18,40)=18*40/(gcd(18,40))=720/2=360

Answer 26

Which was what I said to. ;p

Answer 27

Err too

Answer 28

thats right!
polpak is always right of course lol

Answer 29

Of course! ;p

Answer 30

:)

Answer 31

I just use my calculator, because I roll like that.

Answer 32

thats a cool way to roll

Answer 33

did you make a program for euclid's?

Answer 34

I did...and to find the GCD as a linear combination

Answer 35

can you write programs in your calculator?

Answer 36

what kind do you have polpak?

Answer 37

9*18+(-4)*40=2

Answer 38

Ti 89

Answer 39

ti-nspire cas

Answer 40

nice

Answer 41

i do see word prgm on my calculator maybe you can write programs in ti83

Answer 42

I wrote the program a few weeks ago then I find out that it has the program built in ...oh well ;)

Answer 43

lol writing programs is fun!

Answer 44

Most of my programming is done in Matlab though

Answer 45

i like maple

Answer 46

to program in...never was a big fan.

Answer 47

I love what it can do, but I don't like the programming language

Answer 48

i'm guess i'm just use to it
i still don't know everything about it
i try to implement the rsa with it

Answer 49

I like python

Answer 50

i heard of matlab but not python
i might have to look into that

Answer 51

I'm just started programming in python...seems to be nice

Answer 52

It is quite nice. Certainly my favorite language

Answer 53

you guys are awesome o.O

Answer 54

We know that ;)

Answer 55

lol joe is incredible