There are 141 pupils in a school field.
38 of the boys and
47 of the girls wear spectacles, there are 84 pupils in the school field who do not wear spectacles. How many girls wear spectacles?
| |
Boys |
Girls |
Total |
| Do not wear spectacles |
5 u |
3 p |
84 |
| Wear spectacles |
3 u |
4 p |
57 |
| Total |
8 u |
7 p |
141 |
Number of pupils who wear spectacles
= 141 - 84
= 57
5 u + 3 p = 84 --- (1)
3 u + 4 p = 57 --- (2)
Make u the same.
(1)
x 3 15 u + 9 p = 252 --- (3)
(2)
x 5 15 u + 20 p = 285 --- (4)
(4) - (3)
(15 u + 20 p) - (15 u + 9 p) = 285 - 252
20 p - 9 p = 33
11 p = 33
1 p = 33 ÷ 11 = 3
Number of girls who wear spectacles
= 4 p
= 4 x 3
= 12
Answer(s): 12
