22 Primary 4 pupils and 15 of Primary 5 pupils went on a school camp. The number of Primary 5 girls was 5 times the number of Primary 4 girls, and there were 15 less Primary 5 boys than Primary 4 boys. How many less Primary 5 boys than Primary 5 girls went on the school camp?
| Primary 4 |
Primary 5 |
| 22 |
15 |
| Girls |
Boys |
Girls |
Boys |
| 1 u |
1 p + 15 |
5 u |
1 p |
Total number of pupils in Primary 4 = 1 u + 1 p + 15
1 u + 1 p + 15 = 22
1 u + 1 p = 22 - 15
1 u + 1 p = 7 --- (1)
Total number of pupils in Primary 5 = 5 u + 1 p
5 u + 1 p = 15 --- (2)
(2) - (1)
(5 u + 1 p) - (1 u + 1 p) = 15 - 7
5 u - 1 u = 8
4 u = 8
1 u = 8 ÷ 4 = 2
Number of girls in Primary 5
= 5 u
= 5 x 2
= 10
Number of boys in Primary 5
= 1 p
= 15 - 5 u
= 15 - 10
= 5
Number of less boys than girls in Primary 5
= 10 - 5
= 5
Answer(s): 5
