290 people are in a school.
15 of the females and
110 of the males wear glasses.
33 people wear glasses.
- How many females are there?
- How many males are there?
- How many people do not wear glasses?
|
Number |
Females |
Males |
Total |
290 |
5 u |
10 p |
Wear glasses |
33 |
1 u |
1 p |
No glasses |
|
4 u |
9 p |
(a)
Number of females = 5 u
Number of males = 10 p
5 u + 10 p = 290 --- (1)
1 u + 1 p = 33 --- (2)
(2)
x 5 5 u + 5 p = 165 --- (3)
(1) - (3)
(5 u + 10 p) - (5 u + 5 p) = 290 - 165
5 u + 10 p - 5 u - 5 p = 125
5 p = 125
1 p = 125 ÷ 5 = 25
Substitute 1 p = 25 into (2).
1 u + 1 p = 33
1 u + 25 = 33
1 u = 33 - 25 = 8
Number of females
= 5 u
= 5 x 8
= 40
(b)
Number of males
= 10 p
= 10 x 25
= 250
(c)
Number of females who do not wear glasses
= 5 u - 1 u
= 4 u
Number of males who do not wear glasses
= 10 p - 1 p
= 9 p
Number of people who do not wear glasses
= 290 - 33
= 257
Answer(s): (a) 40; (b) 250; (c) 257