There are between 24 and 40 students in a class
The ratio od boys to girls is 4:7
How many students are in the class?
The ratio between boys and girls is 4/7. This means that the ratio between boys and the total number of students is 4/(7+4)=4/11. Similarily, the ratio between girls and the total number is 7/11.
The the number of students be x. We know that x*4/11=whole number, and that x*7/11=whole number. The only way this can happen is if x is divisible by 11. And the only number divisible by 11 between 24 and 40 is 33, so x=33.
Note that i didnt have to include both numbers 4/11 and 7/11. It would have sufficed to just bring up one of these quotas.
Hope this helped!