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