There are 143 children in a hall.
27 of the boys and
35 of the girls wear watches, there are 88 children in the hall who do not wear watches. How many girls do not wear watches?
| |
Boys |
Girls |
Total |
| Do not wear watches |
5 u |
2 p |
88 |
| Wear watches |
2 u |
3 p |
55 |
| Total |
7 u |
5 p |
143 |
Number of children who wear watches
= 143 - 88
= 55
5 u + 2 p = 88 --- (1)
2 u + 3 p = 55 --- (2)
Make u the same.
(1)
x 2 10 u + 4 p = 176 --- (3)
(2)
x 5 10 u + 15 p = 275 --- (4)
(4) - (3)
(10 u + 15 p) - (10 u + 4 p) = 275 - 176
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
