Ratios are really fractions, so 1 to 3 is really
1/3
it works the same way equivalent fractions do: multiply both numbers (numerator and denominator) by the same number, and the ratio will stay the same. So if we multiply it by 2, we get:
2 to 6
3,
3 to 9
10,
10 to 30
100,
100 to 300