Compare the ratios 2 : 3, 5 : 7, 3 : 4, 5 : 9. Which one is the smallest?

Correct option is A

Given:
2 : 3, 5 : 7, 3 : 4, 5 : 9
Solution:
​$$2 : 3 = \frac{2}{3} = 0.6667 \\\ \\5 : 7 = \frac{5}{7} = 0.7143 \\\ \\3 : 4 = \frac{3}{4} = 0.75 \\\ \\5 : 9 = \frac{5}{9} = 0.5556$$​​
0.6667, 0.7143, 0.75, 0.5556
The smallest decimal value is 0.5556, which corresponds to the ratio 5 : 9.