31 Primary 1 pupils and 23 of Primary 2 pupils went on a school oversea trip. The number of Primary 2 boys was 5 times the number of Primary 1 boys, and there were 20 more Primary 1 girls than Primary 2 girls. How many more Primary 2 boys than Primary 2 girls went on the school oversea trip?
| Primary 1 |
Primary 2 |
| 31 |
23 |
| Boys |
Girls |
Boys |
Girls |
| 1 u |
1 p + 20 |
5 u |
1 p |
Total number of pupils in Primary 1 = 1 u + 1 p + 20
1 u + 1 p + 20 = 31
1 u + 1 p = 31 - 20
1 u + 1 p = 11 --- (1)
Total number of pupils in Primary 2 = 5 u + 1 p
5 u + 1 p = 23 --- (2)
(2) - (1)
(5 u + 1 p) - (1 u + 1 p) = 23 - 11
5 u - 1 u = 12
4 u = 12
1 u = 12 ÷ 4 = 3
Number of boys in Primary 2
= 5 u
= 5 x 3
= 15
Number of girls in Primary 2
= 1 p
= 23 - 5 u
= 23 - 15
= 8
Number of more boys than girls in Primary 2
= 15 - 8
= 7
Answer(s): 7
