There are 154 students in a canteen.
27 of the boys and
35 of the girls wear watches, there are 99 students in the canteen who do not wear watches. How many girls wear watches?
|
Boys |
Girls |
Total |
Do not wear watches |
5 u |
2 p |
99 |
Wear watches |
2 u |
3 p |
55 |
Total |
7 u |
5 p |
154 |
Number of students who wear watches
= 154 - 99
= 55
5 u + 2 p = 99 --- (1)
2 u + 3 p = 55 --- (2)
Make u the same.
(1)
x 2 10 u + 4 p = 198 --- (3)
(2)
x 5 10 u + 15 p = 275 --- (4)
(4) - (3)
(10 u + 15 p) - (10 u + 4 p) = 275 - 198
15 p - 4 p = 77
11 p = 77
1 p = 77 ÷ 11 = 7
Number of girls who wear watches
= 3 p
= 3 x 7
= 21
Answer(s): 21