Question:
The number of boys and girls in a hall was in the ratio 4 : 5.
After 170 boys and 20% of the girls went back to their classrooms, the ratio of the number of boys to the number of girls in the hall became 1 : 2. How many children were there in the hall in the end?
Solution:
![P6 / Nan Hua / 2019 / SA2 / Paper 2 – Q08 [03 marks]](https://i0.wp.com/sgprimaths.com/wp-content/uploads/2020/07/P6_Nan_Hua_2019_Prelims_Paper2_Q08-Qns.jpg?resize=400%2C260&ssl=1)