21 Primary 5 pupils and 17 of Primary 6 pupils went on a school learning journey. The number of Primary 6 boys was 4 times the number of Primary 5 boys, and there were 13 less Primary 6 girls than Primary 5 girls. How many less Primary 6 girls than Primary 6 boys went on the school learning journey?
| Primary 5 |
Primary 6 |
| 21 |
17 |
| Boys |
Girls |
Boys |
Girls |
| 1 u |
1 p + 13 |
4 u |
1 p |
Total number of pupils in Primary 5 = 1 u + 1 p + 13
1 u + 1 p + 13 = 21
1 u + 1 p = 21 - 13
1 u + 1 p = 8 --- (1)
Total number of pupils in Primary 6 = 4 u + 1 p
4 u + 1 p = 17 --- (2)
(2) - (1)
(4 u + 1 p) - (1 u + 1 p) = 17 - 8
4 u - 1 u = 9
3 u = 9
1 u = 9 ÷ 3 = 3
Number of boys in Primary 6
= 4 u
= 4 x 3
= 12
Number of girls in Primary 6
= 1 p
= 17 - 4 u
= 17 - 12
= 5
Number of less girls than boys in Primary 6
= 12 - 5
= 7
Answer(s): 7
