There are 131 pupils in a tuckshop.
38 of the boys and
47 of the girls wear watches, there are 75 pupils in the tuckshop who do not wear watches. How many girls do not wear watches?
| |
Boys |
Girls |
Total |
| Do not wear watches |
5 u |
3 p |
75 |
| Wear watches |
3 u |
4 p |
56 |
| Total |
8 u |
7 p |
131 |
Number of pupils who wear watches
= 131 - 75
= 56
5 u + 3 p = 75 --- (1)
3 u + 4 p = 56 --- (2)
Make u the same.
(1)
x 3 15 u + 9 p = 225 --- (3)
(2)
x 5 15 u + 20 p = 280 --- (4)
(4) - (3)
(15 u + 20 p) - (15 u + 9 p) = 280 - 225
20 p - 9 p = 55
11 p = 55
1 p = 55 ÷ 11 = 5
Number of girls who do not wear watches
= 3 p
= 3 x 5
= 15
Answer(s): 15
