There are 185 pupils in a parade square.
27 of the girls and
35 of the boys wear watches, there are 118 pupils in the parade square who do not wear watches. How many boys do not wear watches?
| |
Girls |
Boys |
Total |
| Do not wear watches |
5 u |
2 p |
118 |
| Wear watches |
2 u |
3 p |
67 |
| Total |
7 u |
5 p |
185 |
Number of pupils who wear watches
= 185 - 118
= 67
5 u + 2 p = 118 --- (1)
2 u + 3 p = 67 --- (2)
Make u the same.
(1)
x 2 10 u + 4 p = 236 --- (3)
(2)
x 5 10 u + 15 p = 335 --- (4)
(4) - (3)
(10 u + 15 p) - (10 u + 4 p) = 335 - 236
15 p - 4 p = 99
11 p = 99
1 p = 99 ÷ 11 = 9
Number of boys who do not wear watches
= 2 p
= 2 x 9
= 18
Answer(s): 18
