Which of the following is the smallest ratio?

Correct option is B

Given:

Ratio given are 15:20, 7:21,21:25, 17:25

Solution:

Solving the ratios:

​$$15:20 =\frac{15}{20} = 0.75$$​​

​$$7:21 = \frac{7}{21} = \frac{1}{3} = 0.333$$​​

​$$21:25 = \frac{21}{25} = 0.84$$​​

​$$17:25 =\frac{17}{25} =0.68$$​​

Hence lowest ratio is 7:21