Register to reply

Greatest common divisor

by matqkks
Tags: maths, number theory
Share this thread:
matqkks
#1
Jun29-13, 02:43 AM
P: 153
Are there any real life applications of the greatest common divisor of two or more integers?
Phys.Org News Partner Mathematics news on Phys.org
'Moral victories' might spare you from losing again
Fair cake cutting gets its own algorithm
Effort to model Facebook yields key to famous math problem (and a prize)
Simon Bridge
#2
Jun29-13, 03:08 AM
Homework
Sci Advisor
HW Helper
Thanks
Simon Bridge's Avatar
P: 12,472
Yes. i.e. whenever you have something depending on a ratio ...

It's not normally expressed in that way though.
Mostly - the lesson is important for the practise it gives in a kind of problem solving.
rexregisanimi
#3
Jun29-13, 03:15 PM
P: 31
There are a whole bunch. I use the idea regularly so it is difficult to point to a specific thing...

Simon Bridge
#4
Jun29-13, 10:58 PM
Homework
Sci Advisor
HW Helper
Thanks
Simon Bridge's Avatar
P: 12,472
Greatest common divisor

Quote Quote by rexregisanimi View Post
There are a whole bunch. I use the idea regularly so it is difficult to point to a specific thing...
Aww go on - show us one... what's the one you use regularly that you last used?
Permanence
#5
Jun30-13, 12:04 AM
P: 48
Here take a look at this Wikipedia article.
https://en.wikipedia.org/wiki/Euclidean_algorithm

Besides all the mathematical applications, I'm sure that you must sometimes call upon the GCD when shopping or possibly even cooking.
rcgldr
#6
Jun30-13, 04:29 AM
HW Helper
P: 7,047
Quote Quote by matqkks View Post
Are there any real life applications of the greatest common divisor of two or more integers?
I can't think of any real world applications. The closest I can think of is the Euclid algorithm for finding the GCD which can be extended and used to find the inverse of a number in finite field, but it's seldom used because there are other and better methods. For example, if the field isn't very large, a lookup table can be used. In the case of hardware implementations of inversion based on "binary" finite fields (which is part of AES encryption), there are complex methods (sub-field mapping) that involve fewer gates than a lookup table. Wiki article for extended Euclid algorithm:

wiki_inverse_in_finite_field.htm
dm164
#7
Jun30-13, 07:15 AM
P: 21
GCD is used any time you want to simplify integers, but have the same ratios as the others have said. Another way to say it is the numbers scale equally. An example is in solving empirical formulas, where you reduce all integers in a chemical formula. Such as hexane C6H8 -> C3H4 GCD(6,8) is 2 so divide each by 2 to get the answer. Though it isn't of much use, but it has a name.
economicsnerd
#8
Jul8-13, 01:58 PM
P: 229
The store sells 8-packs of hotdogs and 12-packs of buns. If you want the same (nonzero) number of each, what's the cheapest way to do it?
Simon Bridge
#9
Jul9-13, 12:51 AM
Homework
Sci Advisor
HW Helper
Thanks
Simon Bridge's Avatar
P: 12,472
@economicsnerd: good example, well done!
Most people wouldn't do that by listing the divisors, but I suppose there are examples less amenable to a bit of trial and error.
Do HS math text books no longer have examples like that these days?
rcgldr
#10
Jul9-13, 03:16 AM
HW Helper
P: 7,047
Quote Quote by economicsnerd View Post
The store sells 8-packs of hotdogs and 12-packs of buns. If you want the same (nonzero) number of each, what's the cheapest way to do it?
Wouldn't this be the "lowest common multiple" as opposed to the "greatest common divisor"?
economicsnerd
#11
Jul9-13, 12:19 PM
P: 229
Quote Quote by rcgldr View Post
Wouldn't this be the "lowest common multiple" as opposed to the "greatest common divisor"?
Directly, I guess it's not really either.
Computing either the GCD or the LCM would get you close to knowing how many bags of each to buy. You either compute {h/GCD(h,b), b/GCD(h,b)} or {LCM(h,b)/h, LCM(h,b)/b}.
Stephen Tashi
#12
Jul9-13, 03:55 PM
Sci Advisor
P: 3,254
If you can think of a real life application of linear Diophantine equations, then the GCD and the Euclidean algorithm have applications to solving those.


Register to reply

Related Discussions
Greatest common divisor. Calculus & Beyond Homework 5
Greatest common divisor Calculus & Beyond Homework 1
Greatest Common Divisor General Math 1
Greatest common divisor Calculus & Beyond Homework 24
Greatest common divisor Calculus & Beyond Homework 19