The number of students in 3 classes is in the ratio 3 : 4 : 5. If 10 students are increased in each class this ratio changes to 4 : 5 : 6. The total number of students in the three classes in the beginning was

Question: The number of students in 3 classes is in the ratio 3 : 4 : 5. If 10 students are increased in each class this ratio changes to 4 : 5 : 6. The total number of students in the three classes in the beginning was

Solution:
Let the number of students in the classes be 3x, 4x and 5x respectively;
Total students = 3x + 4x + 5x = 12x
According to the question,
(3x + 10) : (4x + 10) = 4 : 5
or, 5(3x + 10) = 4(4x+10)
or, 15x + 50 = 16x + 40
or, x = 10

Hence,
Original number of students,
12x = 12 × 10
= 120