LCM of Rational Numbers

J, 3 bytes, non-competing.

*./

Given a list of rational inputs, this folds LCM through it.

Jelly, 19 bytes

g/:@$€Z©Ḣæl/;®Ḣg/$¤

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Python 2, 65 bytes (non-competing)

lambda x:reduce(lambda x,y:x*y/gcd(x,y),x)
from fractions import*

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