290 children are in a school.
15 of the girls and
18 of the boys wear glasses.
43 children wear glasses.
- How many girls are there?
- How many boys are there?
- How many children do not wear glasses?
|
Number |
Girls |
Boys |
Total |
290 |
5 u |
8 p |
Wear glasses |
43 |
1 u |
1 p |
No glasses |
|
4 u |
7 p |
(a)
Number of girls = 5 u
Number of boys = 8 p
5 u + 8 p = 290 --- (1)
1 u + 1 p = 43 --- (2)
(2)
x 5 5 u + 5 p = 215 --- (3)
(1) - (3)
(5 u + 8 p) - (5 u + 5 p) = 290 - 215
5 u + 8 p - 5 u - 5 p = 75
3 p = 75
1 p = 75 ÷ 3 = 25
Substitute 1 p = 25 into (2).
1 u + 1 p = 43
1 u + 25 = 43
1 u = 43 - 25 = 18
Number of girls
= 5 u
= 5 x 18
= 90
(b)
Number of boys
= 8 p
= 8 x 25
= 200
(c)
Number of girls who do not wear glasses
= 5 u - 1 u
= 4 u
Number of boys who do not wear glasses
= 8 p - 1 p
= 7 p
Number of children who do not wear glasses
= 290 - 43
= 247
Answer(s): (a) 90; (b) 200; (c) 247