9514 1404 393
Answer:
33
Step-by-step explanation:
The total number of ratio units is 4+7 = 11. If each one stands for an integer number of students, that number is a multiple of 11 between 24 and 40. The only such number is 3×11 = 33.
There are 33 students in the class.
_____
12 are boys, 21 are girls.
