29 Primary 2 students and 21 of Primary 3 students went on a school oversea trip. The number of Primary 3 girls was 4 times the number of Primary 2 girls, and there were 20 more Primary 2 boys than Primary 3 boys. How many more Primary 3 girls than Primary 3 boys went on the school oversea trip?
Primary 2 |
Primary 3 |
29 |
21 |
Girls |
Boys |
Girls |
Boys |
1 u |
1 p + 20 |
4 u |
1 p |
Total number of students in Primary 2 = 1 u + 1 p + 20
1 u + 1 p + 20 = 29
1 u + 1 p = 29 - 20
1 u + 1 p = 9 --- (1)
Total number of students in Primary 3 = 4 u + 1 p
4 u + 1 p = 21 --- (2)
(2) - (1)
(4 u + 1 p) - (1 u + 1 p) = 21 - 9
4 u - 1 u = 12
3 u = 12
1 u = 12 ÷ 3 = 4
Number of girls in Primary 3
= 4 u
= 4 x 4
= 16
Number of boys in Primary 3
= 1 p
= 21 - 4 u
= 21 - 16
= 5
Number of more girls than boys in Primary 3
= 16 - 5
= 11
Answer(s): 11