24 Primary 5 pupils and 21 of Primary 6 pupils went on a school oversea trip. The number of Primary 6 girls was 5 times the number of Primary 5 girls, and there were 15 more Primary 5 boys than Primary 6 boys. How many less Primary 6 boys than Primary 6 girls went on the school oversea trip?
| Primary 5 |
Primary 6 |
| 24 |
21 |
| Girls |
Boys |
Girls |
Boys |
| 1 u |
1 p + 15 |
5 u |
1 p |
Total number of pupils in Primary 5 = 1 u + 1 p + 15
1 u + 1 p + 15 = 24
1 u + 1 p = 24 - 15
1 u + 1 p = 9 --- (1)
Total number of pupils in Primary 6 = 5 u + 1 p
5 u + 1 p = 21 --- (2)
(2) - (1)
(5 u + 1 p) - (1 u + 1 p) = 21 - 9
5 u - 1 u = 12
4 u = 12
1 u = 12 ÷ 4 = 3
Number of girls in Primary 6
= 5 u
= 5 x 3
= 15
Number of boys in Primary 6
= 1 p
= 21 - 5 u
= 21 - 15
= 6
Number of less boys than girls in Primary 6
= 15 - 6
= 9
Answer(s): 9
