28 Primary 3 students and 22 of Primary 4 students went on a school oversea trip. The number of Primary 4 boys was 4 times the number of Primary 3 boys, and there were 15 less Primary 4 girls than Primary 3 girls. How many less Primary 4 girls than Primary 4 boys went on the school oversea trip?
| Primary 3 |
Primary 4 |
| 28 |
22 |
| Boys |
Girls |
Boys |
Girls |
| 1 u |
1 p + 15 |
4 u |
1 p |
Total number of students in Primary 3 = 1 u + 1 p + 15
1 u + 1 p + 15 = 28
1 u + 1 p = 28 - 15
1 u + 1 p = 13 --- (1)
Total number of students in Primary 4 = 4 u + 1 p
4 u + 1 p = 22 --- (2)
(2) - (1)
(4 u + 1 p) - (1 u + 1 p) = 22 - 13
4 u - 1 u = 9
3 u = 9
1 u = 9 ÷ 3 = 3
Number of boys in Primary 4
= 4 u
= 4 x 3
= 12
Number of girls in Primary 4
= 1 p
= 22 - 4 u
= 22 - 12
= 10
Number of less girls than boys in Primary 4
= 12 - 10
= 2
Answer(s): 2
