There are 181 pupils in a tuckshop.
38 of the girls and
47 of the boys wear watches, there are 109 pupils in the tuckshop who do not wear watches. How many boys wear watches?
| |
Girls |
Boys |
Total |
| Do not wear watches |
5 u |
3 p |
109 |
| Wear watches |
3 u |
4 p |
72 |
| Total |
8 u |
7 p |
181 |
Number of pupils who wear watches
= 181 - 109
= 72
5 u + 3 p = 109 --- (1)
3 u + 4 p = 72 --- (2)
Make u the same.
(1)
x 3 15 u + 9 p = 327 --- (3)
(2)
x 5 15 u + 20 p = 360 --- (4)
(4) - (3)
(15 u + 20 p) - (15 u + 9 p) = 360 - 327
20 p - 9 p = 33
11 p = 33
1 p = 33 ÷ 11 = 3
Number of boys who wear watches
= 4 p
= 4 x 3
= 12
Answer(s): 12
