111 people are in a school.
13 of the males and
15 of the females wear glasses.
33 people wear glasses.
- How many males are there?
- How many females are there?
- How many people do not wear glasses?
|
Number |
Males |
Females |
Total |
111 |
3 u |
5 p |
Wear glasses |
33 |
1 u |
1 p |
No glasses |
|
2 u |
4 p |
(a)
Number of males = 3 u
Number of females = 5 p
3 u + 5 p = 111 --- (1)
1 u + 1 p = 33 --- (2)
(2)
x 3 3 u + 3 p = 99 --- (3)
(1) - (3)
(3 u + 5 p) - (3 u + 3 p) = 111 - 99
3 u + 5 p - 3 u - 3 p = 12
2 p = 12
1 p = 12 ÷ 2 = 6
Substitute 1 p = 6 into (2).
1 u + 1 p = 33
1 u + 6 = 33
1 u = 33 - 6 = 27
Number of males
= 3 u
= 3 x 27
= 81
(b)
Number of females
= 5 p
= 5 x 6
= 30
(c)
Number of males who do not wear glasses
= 3 u - 1 u
= 2 u
Number of females who do not wear glasses
= 5 p - 1 p
= 4 p
Number of people who do not wear glasses
= 111 - 33
= 78
Answer(s): (a) 81; (b) 30; (c) 78