21 Primary 3 pupils and 17 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 14 more Primary 3 girls than Primary 4 girls. How many more Primary 4 boys than Primary 4 girls went on the school camp?
| Primary 3 |
Primary 4 |
| 21 |
17 |
| Boys |
Girls |
Boys |
Girls |
| 1 u |
1 p + 14 |
3 u |
1 p |
Total number of pupils in Primary 3 = 1 u + 1 p + 14
1 u + 1 p + 14 = 21
1 u + 1 p = 21 - 14
1 u + 1 p = 7 --- (1)
Total number of pupils in Primary 4 = 3 u + 1 p
3 u + 1 p = 17 --- (2)
(2) - (1)
(3 u + 1 p) - (1 u + 1 p) = 17 - 7
3 u - 1 u = 10
2 u = 10
1 u = 10 ÷ 2 = 5
Number of boys in Primary 4
= 3 u
= 3 x 5
= 15
Number of girls in Primary 4
= 1 p
= 17 - 3 u
= 17 - 15
= 2
Number of more boys than girls in Primary 4
= 15 - 2
= 13
Answer(s): 13
