20 Primary 2 students and 15 of Primary 3 students went on a school oversea trip. The number of Primary 3 girls was 5 times the number of Primary 2 girls, and there were 13 more Primary 2 boys than Primary 3 boys. How many less Primary 3 boys than Primary 3 girls went on the school oversea trip?
| Primary 2 |
Primary 3 |
| 20 |
15 |
| Girls |
Boys |
Girls |
Boys |
| 1 u |
1 p + 13 |
5 u |
1 p |
Total number of students in Primary 2 = 1 u + 1 p + 13
1 u + 1 p + 13 = 20
1 u + 1 p = 20 - 13
1 u + 1 p = 7 --- (1)
Total number of students in Primary 3 = 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 3
= 5 u
= 5 x 2
= 10
Number of boys in Primary 3
= 1 p
= 15 - 5 u
= 15 - 10
= 5
Number of less boys than girls in Primary 3
= 10 - 5
= 5
Answer(s): 5
