There are 133 students in a canteen.
38 of the girls and
47 of the boys wear spectacles, there are 79 students in the canteen who do not wear spectacles. How many boys wear spectacles?
| |
Girls |
Boys |
Total |
| Do not wear spectacles |
5 u |
3 p |
79 |
| Wear spectacles |
3 u |
4 p |
54 |
| Total |
8 u |
7 p |
133 |
Number of students who wear spectacles
= 133 - 79
= 54
5 u + 3 p = 79 --- (1)
3 u + 4 p = 54 --- (2)
Make u the same.
(1)
x 3 15 u + 9 p = 237 --- (3)
(2)
x 5 15 u + 20 p = 270 --- (4)
(4) - (3)
(15 u + 20 p) - (15 u + 9 p) = 270 - 237
20 p - 9 p = 33
11 p = 33
1 p = 33 ÷ 11 = 3
Number of boys who wear spectacles
= 4 p
= 4 x 3
= 12
Answer(s): 12
