40 Primary 2 students and 35 of Primary 3 students went on a school oversea trip. The number of Primary 3 girls was 3 times the number of Primary 2 girls, and there were 19 less Primary 3 boys than Primary 2 boys. How many less Primary 3 boys than Primary 3 girls went on the school oversea trip?
| Primary 2 |
Primary 3 |
| 40 |
35 |
| Girls |
Boys |
Girls |
Boys |
| 1 u |
1 p + 19 |
3 u |
1 p |
Total number of students in Primary 2 = 1 u + 1 p + 19
1 u + 1 p + 19 = 40
1 u + 1 p = 40 - 19
1 u + 1 p = 21 --- (1)
Total number of students in Primary 3 = 3 u + 1 p
3 u + 1 p = 35 --- (2)
(2) - (1)
(3 u + 1 p) - (1 u + 1 p) = 35 - 21
3 u - 1 u = 14
2 u = 14
1 u = 14 ÷ 2 = 7
Number of girls in Primary 3
= 3 u
= 3 x 7
= 21
Number of boys in Primary 3
= 1 p
= 35 - 3 u
= 35 - 21
= 14
Number of less boys than girls in Primary 3
= 21 - 14
= 7
Answer(s): 7
