24 Primary 4 pupils and 17 of Primary 5 pupils 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 less Primary 5 girls than Primary 4 girls. How many less Primary 5 girls than Primary 5 boys went on the school oversea trip?
| Primary 4 |
Primary 5 |
| 24 |
17 |
| Boys |
Girls |
Boys |
Girls |
| 1 u |
1 p + 15 |
3 u |
1 p |
Total number of pupils in Primary 4 = 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 5 = 3 u + 1 p
3 u + 1 p = 17 --- (2)
(2) - (1)
(3 u + 1 p) - (1 u + 1 p) = 17 - 9
3 u - 1 u = 8
2 u = 8
1 u = 8 ÷ 2 = 4
Number of boys in Primary 5
= 3 u
= 3 x 4
= 12
Number of girls in Primary 5
= 1 p
= 17 - 3 u
= 17 - 12
= 5
Number of less girls than boys in Primary 5
= 12 - 5
= 7
Answer(s): 7
