Which ratio is equivalent to 1 : 5?

Infinite solutions.

Step-by-step explanation:

A ratio, which is essentially a fraction, can be written in an infinite number of ways and still have the same value ...

As an example:

2/1 = 2

6/3 = 2

As long as both the top and bottom of a fraction are multiplied by the same value, the fraction will keep the same value.

So, any ratio that's a multiple of 1/5 is equivalent.