28 Primary 5 students and 23 of Primary 6 students went on a school oversea trip. The number of Primary 6 boys was 3 times the number of Primary 5 boys, and there were 17 more Primary 5 girls than Primary 6 girls. How many less Primary 6 girls than Primary 6 boys went on the school oversea trip?
| Primary 5 |
Primary 6 |
| 28 |
23 |
| Boys |
Girls |
Boys |
Girls |
| 1 u |
1 p + 17 |
3 u |
1 p |
Total number of students in Primary 5 = 1 u + 1 p + 17
1 u + 1 p + 17 = 28
1 u + 1 p = 28 - 17
1 u + 1 p = 11 --- (1)
Total number of students in Primary 6 = 3 u + 1 p
3 u + 1 p = 23 --- (2)
(2) - (1)
(3 u + 1 p) - (1 u + 1 p) = 23 - 11
3 u - 1 u = 12
2 u = 12
1 u = 12 ÷ 2 = 6
Number of boys in Primary 6
= 3 u
= 3 x 6
= 18
Number of girls in Primary 6
= 1 p
= 23 - 3 u
= 23 - 18
= 5
Number of less girls than boys in Primary 6
= 18 - 5
= 13
Answer(s): 13
