There are 124 pupils in a canteen.
38 of the girls and
47 of the boys wear spectacles, there are 72 pupils in the canteen who do not wear spectacles. How many boys do not wear spectacles?
| |
Girls |
Boys |
Total |
| Do not wear spectacles |
5 u |
3 p |
72 |
| Wear spectacles |
3 u |
4 p |
52 |
| Total |
8 u |
7 p |
124 |
Number of pupils who wear spectacles
= 124 - 72
= 52
5 u + 3 p = 72 --- (1)
3 u + 4 p = 52 --- (2)
Make u the same.
(1)
x 3 15 u + 9 p = 216 --- (3)
(2)
x 5 15 u + 20 p = 260 --- (4)
(4) - (3)
(15 u + 20 p) - (15 u + 9 p) = 260 - 216
20 p - 9 p = 44
11 p = 44
1 p = 44 ÷ 11 = 4
Number of boys who do not wear spectacles
= 3 p
= 3 x 4
= 12
Answer(s): 12
