To find the number of students in the school using the ratio of boys in Mr. Martin's class, we can set up a proportion based on the given information.
We know:
- In Mr. Martin's class, there are 18 boys and 32 students total.
- In the school, there are 468 boys, and we need to find the total number of students in the school (let's denote this total as \( s \)).
The ratio of boys to total students in Mr. Martin's class can be expressed as: \[ \frac{18}{32} \]
The ratio of boys to total students in the school is: \[ \frac{468}{s} \]
Since these ratios are proportional, we can set them equal to each other: \[ \frac{18}{32} = \frac{468}{s} \]
This matches option A: A. \( \frac{18}{32} = \frac{s}{468} \)
However, we notice that the variables \( s \) and the arrangement in option A need to be switched around to fit our ratio.
Thus, if we rearranged that to match our needs: \[ \frac{18}{32} = \frac{468}{s} \] would be equivalent to: \[ \frac{18}{32} = \frac{s}{468} \]
Therefore, option A correctly represents the proportion needed to find \( s \): A. \( \frac{18}{32} = \frac{s}{468} \)