39 Primary 4 pupils and 34 of Primary 5 pupils went on a school outing. The number of Primary 5 girls was 3 times the number of Primary 4 girls, and there were 19 less Primary 5 boys than Primary 4 boys. How many less Primary 5 boys than Primary 5 girls went on the school outing?
| Primary 4 |
Primary 5 |
| 39 |
34 |
| Girls |
Boys |
Girls |
Boys |
| 1 u |
1 p + 19 |
3 u |
1 p |
Total number of pupils in Primary 4 = 1 u + 1 p + 19
1 u + 1 p + 19 = 39
1 u + 1 p = 39 - 19
1 u + 1 p = 20 --- (1)
Total number of pupils in Primary 5 = 3 u + 1 p
3 u + 1 p = 34 --- (2)
(2) - (1)
(3 u + 1 p) - (1 u + 1 p) = 34 - 20
3 u - 1 u = 14
2 u = 14
1 u = 14 ÷ 2 = 7
Number of girls in Primary 5
= 3 u
= 3 x 7
= 21
Number of boys in Primary 5
= 1 p
= 34 - 3 u
= 34 - 21
= 13
Number of less boys than girls in Primary 5
= 21 - 13
= 8
Answer(s): 8
