28 Primary 4 students and 25 of Primary 5 students went on a school oversea trip. The number of Primary 5 boys was 3 times the number of Primary 4 boys, and there were 15 more Primary 4 girls than Primary 5 girls. How many more Primary 5 boys than Primary 5 girls went on the school oversea trip?
| Primary 4 |
Primary 5 |
| 28 |
25 |
| Boys |
Girls |
Boys |
Girls |
| 1 u |
1 p + 15 |
3 u |
1 p |
Total number of students in Primary 4 = 1 u + 1 p + 15
1 u + 1 p + 15 = 28
1 u + 1 p = 28 - 15
1 u + 1 p = 13 --- (1)
Total number of students in Primary 5 = 3 u + 1 p
3 u + 1 p = 25 --- (2)
(2) - (1)
(3 u + 1 p) - (1 u + 1 p) = 25 - 13
3 u - 1 u = 12
2 u = 12
1 u = 12 ÷ 2 = 6
Number of boys in Primary 5
= 3 u
= 3 x 6
= 18
Number of girls in Primary 5
= 1 p
= 25 - 3 u
= 25 - 18
= 7
Number of more boys than girls in Primary 5
= 18 - 7
= 11
Answer(s): 11
