# how can I use a while loop for LCM?

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Lorayne Reyes on 12 Jun 2018
Answered: Matt Dickson on 12 Jun 2018
I want to write a program that will allow me to add the value of 'x', and then if the sum is equal to the input for y stop and display that value as the LCM. But, if not, add y+y+y+y.... until x=y.
Paridhi Yadav on 12 Jun 2018
Can you explain clearly what you want ?

Matt Dickson on 12 Jun 2018
To do it iteratively as you laid out, you'd have something like
function [leastCommon] = lcm(a,b)
a1 = a;
b2 = b;
while a1 ~= b1
if a1 > b1
b1 = b1 + b;
else
a1 = a1 + a;
end
end
leastCommon = a1;
end
I'm not sure if you're set on doing it the way you described, but a simpler way to find the LCM is to use the greatest common division (GCD). Say you want to know the LCM of two numbers, a and b. Then
LCM = (a * b) / gcd(a,b)
The GCD is easy to find via the Euclidean algorithm, which is recursively defined as
function [ret] = gcd(a, b)
if b == 0
ret = a;
else
ret = gcd(b, mod(a, b));
end