24 Primary 4 students and 17 of Primary 5 students went on a school trip. The number of Primary 5 girls was 5 times the number of Primary 4 girls, and there were 19 less Primary 5 boys than Primary 4 boys. How many less Primary 5 boys than Primary 5 girls went on the school trip?

Primary 4		Primary 5
24		17
Girls	Boys	Girls	Boys
1 u	1 p + 19	5  u	1 p

Total number of students in Primary 4 = 1 u + 1 p + 19

1 u + 1 p + 19 = 24
1 u + 1 p = 24 - 19
1 u + 1 p = 5 --- (1)

Total number of students in Primary 5 = 5 u + 1 p

5 u + 1 p = 17 --- (2)

(2) - (1)
(5 u + 1 p) - (1 u + 1 p) = 17 - 5
5 u - 1 u = 12
4 u = 12

1 u = 12 ÷ 4 = 3

Number of girls in Primary 5
= 5 u
= 5 x 3
= 15

Number of boys in Primary 5
= 1 p
= 17 - 5 u
= 17 - 15
= 2

Number of less boys than girls in Primary 5
= 15 - 2
= 13

Answer(s): 13