158 children are in a school.
14 of the girls and
16 of the boys wear glasses.
29 children wear glasses.
- How many girls are there?
- How many boys are there?
- How many children do not wear glasses?
|
Number |
Girls |
Boys |
Total |
158 |
4 u |
6 p |
Wear glasses |
29 |
1 u |
1 p |
No glasses |
|
3 u |
5 p |
(a)
Number of girls = 4 u
Number of boys = 6 p
4 u + 6 p = 158 --- (1)
1 u + 1 p = 29 --- (2)
(2)
x 4 4 u + 4 p = 116 --- (3)
(1) - (3)
(4 u + 6 p) - (4 u + 4 p) = 158 - 116
4 u + 6 p - 4 u - 4 p = 42
2 p = 42
1 p = 42 ÷ 2 = 21
Substitute 1 p = 21 into (2).
1 u + 1 p = 29
1 u + 21 = 29
1 u = 29 - 21 = 8
Number of girls
= 4 u
= 4 x 8
= 32
(b)
Number of boys
= 6 p
= 6 x 21
= 126
(c)
Number of girls who do not wear glasses
= 4 u - 1 u
= 3 u
Number of boys who do not wear glasses
= 6 p - 1 p
= 5 p
Number of children who do not wear glasses
= 158 - 29
= 129
Answer(s): (a) 32; (b) 126; (c) 129