265 people are in a school.
13 of the females and
17 of the males wear glasses.
47 people wear glasses.
- How many females are there?
- How many males are there?
- How many people do not wear glasses?
|
Number |
Females |
Males |
Total |
265 |
3 u |
7 p |
Wear glasses |
47 |
1 u |
1 p |
No glasses |
|
2 u |
6 p |
(a)
Number of females = 3 u
Number of males = 7 p
3 u + 7 p = 265 --- (1)
1 u + 1 p = 47 --- (2)
(2)
x 3 3 u + 3 p = 141 --- (3)
(1) - (3)
(3 u + 7 p) - (3 u + 3 p) = 265 - 141
3 u + 7 p - 3 u - 3 p = 124
4 p = 124
1 p = 124 ÷ 4 = 31
Substitute 1 p = 31 into (2).
1 u + 1 p = 47
1 u + 31 = 47
1 u = 47 - 31 = 16
Number of females
= 3 u
= 3 x 16
= 48
(b)
Number of males
= 7 p
= 7 x 31
= 217
(c)
Number of females who do not wear glasses
= 3 u - 1 u
= 2 u
Number of males who do not wear glasses
= 7 p - 1 p
= 6 p
Number of people who do not wear glasses
= 265 - 47
= 218
Answer(s): (a) 48; (b) 217; (c) 218