How can 1 number be a ratio?

3/6

Step-by-step explanation:The most common way to write a ratio is as a fraction, 3/6. We could also write it using the word "to," as "3 to 6." Finally, we could write this ratio using a colon between the two numbers, 3:6. Be sure you understand that these are all ways to write the same number.

its 4 because 2 times 2 is 4, if you double the number two you get four

i hope this is what you were looking for.

see attached graph