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 / Raffles Girls / 2019 / SA2 / Paper 1 – Q24 [2 marks]](https://i0.wp.com/sgprimaths.com/wp-content/uploads/2022/07/P6_SA2_2019_Raffles_Paper1_Q24-Qns.jpg?resize=400%2C164&ssl=1)
![P6 / Maris Stella / 2020 / SA2 Prelims / Paper 1 – Q15 [2 marks]](https://i0.wp.com/sgprimaths.com/wp-content/uploads/2021/12/P6_SA2_2020_Maris_Stella_Paper1_Q15-Qns.jpg?resize=400%2C260&ssl=1)