Question 277964
let b = number of boys
let g = number of girls.


In Mr. Smith's class, g = 3*b


In Ms. Perry's class, b = 2*g


Mr. smith has 60 students in his class.


Ms. Perry has 45 students in her class.


Combine the classes and what is the ratio of boys to girls?


in Mr. Smith's class, you have:


b + g = 60


Since g = 3*b, you get:


b + 3*b = 60 which becomes:


4*b = 60 which becomes:


b = 15


You have 15 boys and 45 girls in Mr. Smith's class.


The number of girls is 3 * the number of boys which is correct.


In Ms. Perry's class, you have:


b + g = 45


Since b = 2*g, this becomes:


2*g + g = 45 which becomes:


3*g = 45 which becomes:


g = 15


Ms. Perry has 30 boys and 15 girls.


The number of boys is 2 * the number of girls which is correct.


So, you have:


15 boys and 45 girls in Mr. Smith's class.
30 boys and 15 girls in Ms. Perry's class.


When you combine the classes, you have:


45 boys and 60 girls for a total of 105 students.


The ratio of boys to girls is equal to:


45/60 = .75


That would be the same as 3:4 which is selection A.