# It's ok to use decimals in fractions

Submitted by onevest in just_post

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# flabberghaster wrote at April 14, 2019, 3:41 PM

Yes, a fraction is a rational number. The rational numbers are the set Q such that for all x in Q, x = a/b for some integer a and b (b != 0).

Decimal notation is just a different way to write a rational number.

Since Q is closed under division meaning that a rational divided by a rational is guaranteed to return a rational number (except for division by zero), then having a fraction with a decimal in it is valid.

# bunnies wrote at April 15, 2019, 5:00 PM

Yes, a fraction is a rational number.

Is this actually true? 1/(2*pi) seems like a perfectly reasonable fraction to me. My intuitive feeling is that a fraction is just one quantity divided by another quantity, no matter the set membership.

# flabberghaster wrote at April 16, 2019, 12:04 AM

Oh i thought i remembered them as being rational, and that irrational ones were invalid. But i was wrong.

Flabbergaster demolished by logic and reason