ratio expressions which are correct

If a:b=1:2, which of the following would be correct?

a) The ratio of a and b is 1:2
b) The ratio of a to b is 1:2
c) The a to b ratio is 1:2.
d) The ratio of the two variables is 1:2
e) The ratio between the two variables is 1:2
f) The a:b ratio is 1:2.
g) The ratio of a and b is 0.5
h) The ratio of a to b is 0.5
i) The a to b ratio is 0.5.
j) The ratio of the two variables is 0.5
k) The ratio between the two variables is 0.5
l) The a:b ratio is 0.5.

It's this simple:

a) The ratio of a and b is 1:2  WRONG
b) The ratio of a to b is 1:2  OK
c) The a to b ratio is 1:2.  OK
d) The ratio of the two variables is 1:2  WRONG
e) The ratio between the two variables is 1:2  OK
f) The a:b ratio is 1:2.  OK
g) The ratio of a and b is 0.5  WRONG
h) The ratio of a to b is 0.5  OK
i) The a to b ratio is 0.5.  OK
j) The ratio of the two variables is 0.5  WRONG
k) The ratio between the two variables is 0.5  OK
l) The a:b ratio is 0.5.  OK

A ratio is a "thing"; indeed it exists "between" two values.

(You could certainly use alternates to "between" .. such as "in relation to" "with regard to" and so on ... but "between" is perfect.)

This applies to anything which exists in relation to "two values."

For example, consider difference.

Hence, "the difference between six and eight is two." Note that "the difference of six and eight..." is meaningless.

Exactly the same with, say distance.

"The distance from Nashville to Atlanta is 250 miles." Note that the phrase "The distance of Nashville and Atlanta..." is meaningless.

And: it's perfectly OK to use the pair as a naming adjective: so...

The big distance
The amazing distance
The small distance
The Nashville/Atlanta distance
The Nashville-Atlanta distance
The "Nashville, Atlanta" distance
The a/b ratio
The a,b ratio
The "a,b" ratio

.. all work.

No mystery here.