A certain class has 24 students. Which of the following could NOT be the ratio of boys to girls?

2:3

1:1

1:2

3:5

5:7

The ratio of 2:3 will not work. this is because when you add up all the parts of the ratio it should make a factor of 24. 2+3=5 which will not divide evenly into 24 whereas all the others will

2:3 is the answer to your question