# lcm and gcd using a calculator

Discussion in 'Math' started by Eric007, Sep 29, 2013.

1. ### Eric007 Thread Starter Senior Member

Aug 5, 2011
1,055
33
Hey guyz,

Was wondering if anyone here knows how to compute the gcd and lcm of a set of numbers (let's say 3 or 4 numbers or...) using a scientific calculator that does NOT have those functions?

BTW, gcd = greatest common divisor and lcm = least common multiple.

I know how to compute it manually (by hand) but for large numbers it takes time.

Thanks!

Last edited: Sep 29, 2013
2. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
If you had ever used a slide rule it would be easy, you had to keep the exponent in your head with those.

3. ### WBahn Moderator

Mar 31, 2012
18,092
4,918
I would imagine that you can find the LCD/LCM of the first two (LCD using the Euclidean Algorithm) and then the LCD/LCM of the result and the next value and proceed like that. That should be pretty efficient, at least for the LCD, since it is going to bound very quickly. I think the LCM will behave similarly.

Eric007 likes this.
4. ### Tesla23 Active Member

May 10, 2009
323
67
By hand - no better way than to use the associativity of LCM and GCD as WBahn suggests.

Otherwise, use Wolfram Alpha that lets you type
gcd(n1, n2, n3...) and lcm(n1, n2, n3..) and it will work it out.

Eric007 likes this.