79 children are in a school.
13 of the boys and
110 of the girls wear glasses.
24 children wear glasses.
- How many boys are there?
- How many girls are there?
- How many children do not wear glasses?
|
Number |
Boys |
Girls |
Total |
79 |
3 u |
10 p |
Wear glasses |
24 |
1 u |
1 p |
No glasses |
|
2 u |
9 p |
(a)
Number of boys = 3 u
Number of girls = 10 p
3 u + 10 p = 79 --- (1)
1 u + 1 p = 24 --- (2)
(2)
x 3 3 u + 3 p = 72 --- (3)
(1) - (3)
(3 u + 10 p) - (3 u + 3 p) = 79 - 72
3 u + 10 p - 3 u - 3 p = 7
7 p = 7
1 p = 7 ÷ 7 = 1
Substitute 1 p = 1 into (2).
1 u + 1 p = 24
1 u + 1 = 24
1 u = 24 - 1 = 23
Number of boys
= 3 u
= 3 x 23
= 69
(b)
Number of girls
= 10 p
= 10 x 1
= 10
(c)
Number of boys who do not wear glasses
= 3 u - 1 u
= 2 u
Number of girls who do not wear glasses
= 10 p - 1 p
= 9 p
Number of children who do not wear glasses
= 79 - 24
= 55
Answer(s): (a) 69; (b) 10; (c) 55