There are 145 pupils in a parade square.
27 of the boys and
35 of the girls wear watches, there are 91 pupils in the parade square who do not wear watches. How many girls do not wear watches?
| |
Boys |
Girls |
Total |
| Do not wear watches |
5 u |
2 p |
91 |
| Wear watches |
2 u |
3 p |
54 |
| Total |
7 u |
5 p |
145 |
Number of pupils who wear watches
= 145 - 91
= 54
5 u + 2 p = 91 --- (1)
2 u + 3 p = 54 --- (2)
Make u the same.
(1)
x 2 10 u + 4 p = 182 --- (3)
(2)
x 5 10 u + 15 p = 270 --- (4)
(4) - (3)
(10 u + 15 p) - (10 u + 4 p) = 270 - 182
15 p - 4 p = 88
11 p = 88
1 p = 88 ÷ 11 = 8
Number of girls who do not wear watches
= 2 p
= 2 x 8
= 16
Answer(s): 16
