There are 146 pupils in a hall.
38 of the girls and
47 of the boys wear caps, there are 83 pupils in the hall who do not wear caps. How many boys do not wear caps?
| |
Girls |
Boys |
Total |
| Do not wear caps |
5 u |
3 p |
83 |
| Wear caps |
3 u |
4 p |
63 |
| Total |
8 u |
7 p |
146 |
Number of pupils who wear caps
= 146 - 83
= 63
5 u + 3 p = 83 --- (1)
3 u + 4 p = 63 --- (2)
Make u the same.
(1)
x 3 15 u + 9 p = 249 --- (3)
(2)
x 5 15 u + 20 p = 315 --- (4)
(4) - (3)
(15 u + 20 p) - (15 u + 9 p) = 315 - 249
20 p - 9 p = 66
11 p = 66
1 p = 66 ÷ 11 = 6
Number of boys who do not wear caps
= 3 p
= 3 x 6
= 18
Answer(s): 18
