There are 195 pupils in a hall.
38 of the boys and
47 of the girls wear spectacles, there are 115 pupils in the hall who do not wear spectacles. How many girls do not wear spectacles?
| |
Boys |
Girls |
Total |
| Do not wear spectacles |
5 u |
3 p |
115 |
| Wear spectacles |
3 u |
4 p |
80 |
| Total |
8 u |
7 p |
195 |
Number of pupils who wear spectacles
= 195 - 115
= 80
5 u + 3 p = 115 --- (1)
3 u + 4 p = 80 --- (2)
Make u the same.
(1)
x 3 15 u + 9 p = 345 --- (3)
(2)
x 5 15 u + 20 p = 400 --- (4)
(4) - (3)
(15 u + 20 p) - (15 u + 9 p) = 400 - 345
20 p - 9 p = 55
11 p = 55
1 p = 55 ÷ 11 = 5
Number of girls who do not wear spectacles
= 3 p
= 3 x 5
= 15
Answer(s): 15
