Question 12
70% of the pupils in a hall were boys. When 108 boys had left the hall, the number of girls was three times the number of boys remaining in the hall. Find the original of pupils in the hall.
**Editorial note for this self-study exercise:** Only the stated 108 boys leave; no girls leave and nobody enters. The last sentence asks for the original number of pupils.
**Editorial note for this self-study exercise:** Only the stated 108 boys leave; no girls leave and nobody enters. The last sentence asks for the original number of pupils.