There are 215 pupils in a hall.
38 of the girls and
47 of the boys wear hats, there are 122 pupils in the hall who do not wear hats. How many boys wear hats?
|
Girls |
Boys |
Total |
Do not wear hats |
5 u |
3 p |
122 |
Wear hats |
3 u |
4 p |
93 |
Total |
8 u |
7 p |
215 |
Number of pupils who wear hats
= 215 - 122
= 93
5 u + 3 p = 122 --- (1)
3 u + 4 p = 93 --- (2)
Make u the same.
(1)
x 3 15 u + 9 p = 366 --- (3)
(2)
x 5 15 u + 20 p = 465 --- (4)
(4) - (3)
(15 u + 20 p) - (15 u + 9 p) = 465 - 366
20 p - 9 p = 99
11 p = 99
1 p = 99 ÷ 11 = 9
Number of boys who wear hats
= 4 p
= 4 x 9
= 36
Answer(s): 36