There are 161 pupils in a school field.
27 of the girls and
35 of the boys wear watches, there are 104 pupils in the school field who do not wear watches. How many boys do not wear watches?
| |
Girls |
Boys |
Total |
| Do not wear watches |
5 u |
2 p |
104 |
| Wear watches |
2 u |
3 p |
57 |
| Total |
7 u |
5 p |
161 |
Number of pupils who wear watches
= 161 - 104
= 57
5 u + 2 p = 104 --- (1)
2 u + 3 p = 57 --- (2)
Make u the same.
(1)
x 2 10 u + 4 p = 208 --- (3)
(2)
x 5 10 u + 15 p = 285 --- (4)
(4) - (3)
(10 u + 15 p) - (10 u + 4 p) = 285 - 208
15 p - 4 p = 77
11 p = 77
1 p = 77 ÷ 11 = 7
Number of boys who do not wear watches
= 2 p
= 2 x 7
= 14
Answer(s): 14
