Question

The students in three classes are in the ratio 2:3:5. if 20 students are increased in each class, the ratio changes to 4:5:7. the total no. of students before the increases were.

Answer 1

There are three classes.
Ratios of the students of three classes are = 2:3:5

Let number of students in first class be 2x
number of students in second class be 3x
number of students in third class be 5x

(According to the question)
20 students are increased in each class and the ratio becomes 4:5:7

so,
1st class = (2x+20) = 4x
2nd class = (3x+20) = 5x
3rd class = (5x+20) = 7x

Students in 1st class = (2x+20) = 4x
=> 20 = 4x-2x
=> 20 = 2x
=> 20/2 = x
=> 10 = x

Students in 2nd class = (3x+20) = 5x
=> 3x+20 = 5x
=> 20 = 5x-3x
=> 20 = 2x
=> 20/2 = x
=> 10 = x

Students in 3rd class = (5x+20) = 7x
=> 5x+20 = 7x
=> 20 = 7x-5x
=> 20 = 2x
=> 20/2 = x
=> 10 = x

Total number of students before 20 were increase tree classes students were in ratio 2:3:5

1st class = 2x = 2*10 = 20
2nd class = 3x = 3*10 = 30
3rd class = 5x = 5*10 = 50

Hence,
1st class = 20 students,
2nd class = 30 students,
3rd class = 50 students.

Answer 2

Answer:

Step-by-step explanation:

This is the answer in a short and easy method which has less chances of making mistakes. It was an interesting question....Hope it helps.....