29 Primary 3 pupils and 24 of Primary 4 pupils went on a school camp. The number of Primary 4 boys was 3 times the number of Primary 3 boys, and there were 17 less Primary 4 girls than Primary 3 girls. How many less Primary 4 girls than Primary 4 boys went on the school camp?
| Primary 3 |
Primary 4 |
| 29 |
24 |
| Boys |
Girls |
Boys |
Girls |
| 1 u |
1 p + 17 |
3 u |
1 p |
Total number of pupils in Primary 3 = 1 u + 1 p + 17
1 u + 1 p + 17 = 29
1 u + 1 p = 29 - 17
1 u + 1 p = 12 --- (1)
Total number of pupils in Primary 4 = 3 u + 1 p
3 u + 1 p = 24 --- (2)
(2) - (1)
(3 u + 1 p) - (1 u + 1 p) = 24 - 12
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
= 24 - 3 u
= 24 - 18
= 6
Number of less girls than boys in Primary 4
= 18 - 6
= 12
Answer(s): 12
