There are 171 children in a parade square.
27 of the boys and
35 of the girls wear watches, there are 108 children 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 |
108 |
| Wear watches |
2 u |
3 p |
63 |
| Total |
7 u |
5 p |
171 |
Number of children who wear watches
= 171 - 108
= 63
5 u + 2 p = 108 --- (1)
2 u + 3 p = 63 --- (2)
Make u the same.
(1)
x 2 10 u + 4 p = 216 --- (3)
(2)
x 5 10 u + 15 p = 315 --- (4)
(4) - (3)
(10 u + 15 p) - (10 u + 4 p) = 315 - 216
15 p - 4 p = 99
11 p = 99
1 p = 99 ÷ 11 = 9
Number of girls who do not wear watches
= 2 p
= 2 x 9
= 18
Answer(s): 18
