33 Primary 2 students and 30 of Primary 3 students went on a school camp. The number of Primary 3 girls was 4 times the number of Primary 2 girls, and there were 18 more Primary 2 boys than Primary 3 boys. How many less Primary 3 boys than Primary 3 girls went on the school camp?
| Primary 2 |
Primary 3 |
| 33 |
30 |
| Girls |
Boys |
Girls |
Boys |
| 1 u |
1 p + 18 |
4 u |
1 p |
Total number of students in Primary 2 = 1 u + 1 p + 18
1 u + 1 p + 18 = 33
1 u + 1 p = 33 - 18
1 u + 1 p = 15 --- (1)
Total number of students in Primary 3 = 4 u + 1 p
4 u + 1 p = 30 --- (2)
(2) - (1)
(4 u + 1 p) - (1 u + 1 p) = 30 - 15
4 u - 1 u = 15
3 u = 15
1 u = 15 ÷ 3 = 5
Number of girls in Primary 3
= 4 u
= 4 x 5
= 20
Number of boys in Primary 3
= 1 p
= 30 - 4 u
= 30 - 20
= 10
Number of less boys than girls in Primary 3
= 20 - 10
= 10
Answer(s): 10
