There are 137 pupils in a school field.
38 of the boys and
47 of the girls wear scarves, there are 76 pupils in the school field who do not wear scarves. How many girls do not wear scarves?
| |
Boys |
Girls |
Total |
| Do not wear scarves |
5 u |
3 p |
76 |
| Wear scarves |
3 u |
4 p |
61 |
| Total |
8 u |
7 p |
137 |
Number of pupils who wear scarves
= 137 - 76
= 61
5 u + 3 p = 76 --- (1)
3 u + 4 p = 61 --- (2)
Make u the same.
(1)
x 3 15 u + 9 p = 228 --- (3)
(2)
x 5 15 u + 20 p = 305 --- (4)
(4) - (3)
(15 u + 20 p) - (15 u + 9 p) = 305 - 228
20 p - 9 p = 77
11 p = 77
1 p = 77 ÷ 11 = 7
Number of girls who do not wear scarves
= 3 p
= 3 x 7
= 21
Answer(s): 21
