There are 188 pupils in a parade square.
38 of the boys and
47 of the girls wear watches, there are 112 pupils in the parade square who do not wear watches. How many girls wear watches?
| |
Boys |
Girls |
Total |
| Do not wear watches |
5 u |
3 p |
112 |
| Wear watches |
3 u |
4 p |
76 |
| Total |
8 u |
7 p |
188 |
Number of pupils who wear watches
= 188 - 112
= 76
5 u + 3 p = 112 --- (1)
3 u + 4 p = 76 --- (2)
Make u the same.
(1)
x 3 15 u + 9 p = 336 --- (3)
(2)
x 5 15 u + 20 p = 380 --- (4)
(4) - (3)
(15 u + 20 p) - (15 u + 9 p) = 380 - 336
20 p - 9 p = 44
11 p = 44
1 p = 44 ÷ 11 = 4
Number of girls who wear watches
= 4 p
= 4 x 4
= 16
Answer(s): 16
