36 Primary 4 students and 33 of Primary 5 students went on a school camp. The number of Primary 5 girls was 4 times the number of Primary 4 girls, and there were 18 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 |
| 36 |
33 |
| Girls |
Boys |
Girls |
Boys |
| 1 u |
1 p + 18 |
4 u |
1 p |
Total number of students in Primary 4 = 1 u + 1 p + 18
1 u + 1 p + 18 = 36
1 u + 1 p = 36 - 18
1 u + 1 p = 18 --- (1)
Total number of students in Primary 5 = 4 u + 1 p
4 u + 1 p = 33 --- (2)
(2) - (1)
(4 u + 1 p) - (1 u + 1 p) = 33 - 18
4 u - 1 u = 15
3 u = 15
1 u = 15 ÷ 3 = 5
Number of girls in Primary 5
= 4 u
= 4 x 5
= 20
Number of boys in Primary 5
= 1 p
= 33 - 4 u
= 33 - 20
= 13
Number of less boys than girls in Primary 5
= 20 - 13
= 7
Answer(s): 7
