Girls 1, boys 4, * * 5.
55% of the total number of people: 5x55% = 2.75 (copies)
Each serving: 100(4-2.75)= 80 (person)
Participate in this competition * * *: 80x5=400 (person)
The ratio of girls to boys is 1:4.
Boys account for 4/( 1+4)=4/5 of the participants.
Total number of people: 100(4/5-55%)= 400 (people)