36 Primary 3 students and 30 of Primary 4 students went on a school learning journey. The number of Primary 4 girls was 3 times the number of Primary 3 girls, and there were 20 less Primary 4 boys than Primary 3 boys. How many less Primary 4 boys than Primary 4 girls went on the school learning journey?
| Primary 3 |
Primary 4 |
| 36 |
30 |
| Girls |
Boys |
Girls |
Boys |
| 1 u |
1 p + 20 |
3 u |
1 p |
Total number of students in Primary 3 = 1 u + 1 p + 20
1 u + 1 p + 20 = 36
1 u + 1 p = 36 - 20
1 u + 1 p = 16 --- (1)
Total number of students in Primary 4 = 3 u + 1 p
3 u + 1 p = 30 --- (2)
(2) - (1)
(3 u + 1 p) - (1 u + 1 p) = 30 - 16
3 u - 1 u = 14
2 u = 14
1 u = 14 ÷ 2 = 7
Number of girls in Primary 4
= 3 u
= 3 x 7
= 21
Number of boys in Primary 4
= 1 p
= 30 - 3 u
= 30 - 21
= 9
Number of less boys than girls in Primary 4
= 21 - 9
= 12
Answer(s): 12
