Answer:
Convert these ratios into fractions and then into their actual values.
(This is just one way of solving this, there are other plentiful ways you could use to solve this.)
2 : 9
Will become
2/9
Which will result in
0.222...
3 : 18
Will become
3/18
Which will result in
0.1666...
1 : 3
Will become
1/3
Which will result in
0.333...
Now, compare these numbers:-
0.222..., 0.1666..., and 0.333...
And out of these three numbers, 0.333... is by far the greatest number out of all of these ratios.
Therefore, the ratio 1:3 is the largest ratio.