[R] cancelling in fraction

[capybara!]

Dear All,

I have a fraction of 60./(220.*6.), which equals 1./22.
My question is how to cancel the fraction so I actually get 1/22 (actually I
just need the factor 22) using R. I tried it with prime factor decomposition
from the package "schoolmath":

> require("schoolmath")
Loading required package: schoolmath
> nom <- prime.factor(60)
> nom
[1] 2 2 3 5
> denom <- prime.factor(220 * 6)
> denom
[1]  2  2  2  3  5 11

So far so good, now I just need to take all elements which are in nom out of
denom (if possible).
For this I use the package "sets", its function set_complement should
exactly do that, but:

> require(sets)
> set_complement(nom, denom)
{2, 2, 11}

It gives me {2,2,11} and 2 * 2 * 11 is 44 and not 22.
What am I doing wrong? Can anybody help me? 
Is there maybe a more elegant way to cancel a fraction than by prime factor
decomposition?

Many thanks in advance,

Hannes


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