201 children are in a school.
13 of the boys and
19 of the girls wear glasses.
39 children wear glasses.
- How many boys are there?
- How many girls are there?
- How many children do not wear glasses?
|
Number |
Boys |
Girls |
Total |
201 |
3 u |
9 p |
Wear glasses |
39 |
1 u |
1 p |
No glasses |
|
2 u |
8 p |
(a)
Number of boys = 3 u
Number of girls = 9 p
3 u + 9 p = 201 --- (1)
1 u + 1 p = 39 --- (2)
(2)
x 3 3 u + 3 p = 117 --- (3)
(1) - (3)
(3 u + 9 p) - (3 u + 3 p) = 201 - 117
3 u + 9 p - 3 u - 3 p = 84
6 p = 84
1 p = 84 ÷ 6 = 14
Substitute 1 p = 14 into (2).
1 u + 1 p = 39
1 u + 14 = 39
1 u = 39 - 14 = 25
Number of boys
= 3 u
= 3 x 25
= 75
(b)
Number of girls
= 9 p
= 9 x 14
= 126
(c)
Number of boys who do not wear glasses
= 3 u - 1 u
= 2 u
Number of girls who do not wear glasses
= 9 p - 1 p
= 8 p
Number of children who do not wear glasses
= 201 - 39
= 162
Answer(s): (a) 75; (b) 126; (c) 162