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 / Temasek / 2020 / SA2 Prelims / Paper 2 – Q16 [4 marks]](https://i0.wp.com/sgprimaths.com/wp-content/uploads/2020/09/P6_Temasek_2020_SA2_Paper2_Q16-Qns.jpg?resize=400%2C260&ssl=1)
![P6 / Nanyang / 2019 / CA1 / Paper 2 – Q15 [4 marks]](https://i0.wp.com/sgprimaths.com/wp-content/uploads/2022/04/P6_CA1_2019_Nanyang_Paper2_Q15-Qns.jpg?resize=400%2C260&ssl=1)