26 Primary 3 pupils and 23 of Primary 4 pupils went on a school trip. The number of Primary 4 boys was 3 times the number of Primary 3 boys, and there were 15 less Primary 4 girls than Primary 3 girls. How many less Primary 4 girls than Primary 4 boys went on the school trip?
| Primary 3 |
Primary 4 |
| 26 |
23 |
| Boys |
Girls |
Boys |
Girls |
| 1 u |
1 p + 15 |
3 u |
1 p |
Total number of pupils in Primary 3 = 1 u + 1 p + 15
1 u + 1 p + 15 = 26
1 u + 1 p = 26 - 15
1 u + 1 p = 11 --- (1)
Total number of pupils in Primary 4 = 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 4
= 3 u
= 3 x 6
= 18
Number of girls in Primary 4
= 1 p
= 23 - 3 u
= 23 - 18
= 5
Number of less girls than boys in Primary 4
= 18 - 5
= 13
Answer(s): 13
