Positive integers 30, 72, and N have the property that the product of any two of them is divisible by the third. What is the smallest possible value of N?(adsbygoogle = window.adsbygoogle || []).push({});

Note I have not yet taken a Number Theory course.

I think I have found the solution using a bit of reasoning and some luck. N=60? I figured N could not be smaller than the gcd of 30 and 72, and could not be greater than their product. I also found a pattern for (30N)/72. Inputting 10, 15, 20, 30 for N gave a result of 25/6, 25/4, 25/3, 25/2, respectively. I figured that this converged to 25/1, which would then be my solution. N=60 indeed yields 25/1.

However, I feel that this is closer to luck than anything else, and also it is not very elegant. Can someone show me another way of doing this, perhaps something more elegant?

-F

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Simple Number Theory Problem

**Physics Forums | Science Articles, Homework Help, Discussion**