133 children are in a school.
14 of the girls and
19 of the boys wear glasses.
27 children wear glasses.
- How many girls are there?
- How many boys are there?
- How many children do not wear glasses?
|
Number |
Girls |
Boys |
Total |
133 |
4 u |
9 p |
Wear glasses |
27 |
1 u |
1 p |
No glasses |
|
3 u |
8 p |
(a)
Number of girls = 4 u
Number of boys = 9 p
4 u + 9 p = 133 --- (1)
1 u + 1 p = 27 --- (2)
(2)
x 4 4 u + 4 p = 108 --- (3)
(1) - (3)
(4 u + 9 p) - (4 u + 4 p) = 133 - 108
4 u + 9 p - 4 u - 4 p = 25
5 p = 25
1 p = 25 ÷ 5 = 5
Substitute 1 p = 5 into (2).
1 u + 1 p = 27
1 u + 5 = 27
1 u = 27 - 5 = 22
Number of girls
= 4 u
= 4 x 22
= 88
(b)
Number of boys
= 9 p
= 9 x 5
= 45
(c)
Number of girls who do not wear glasses
= 4 u - 1 u
= 3 u
Number of boys who do not wear glasses
= 9 p - 1 p
= 8 p
Number of children who do not wear glasses
= 133 - 27
= 106
Answer(s): (a) 88; (b) 45; (c) 106