PSLE Michael had black pencils and green pencils for sale. He sold 60 black pencils. 40% of the pencils sold were green.
- How many black pencils and green pencils did Michael sell altogether?
- He sold 50% of his pencils. 70% of the pencils left unsold were black. How many green pencils did Michael have at first?
| |
Black |
Green |
Total |
Total in percent |
| Before |
6.5 u |
3.5 u |
10 u |
100% |
| Change |
- 60%
- 3 u |
- 40%
- 2 u |
- 100%
- 5 u |
- 50% |
| After |
70%
3.5 u |
30%
1.5 u |
100%
5 u |
50%
|
40% =
40100 =
25 Total number of pencils sold = 5 u
Number of green pencils sold = 2 u
Number of black pencils sold
= 5 u - 2 u
= 3 u
3 u = 60
1 u = 60 ÷ 3 = 20
Total number of pencils sold
= 5 u
= 5 x 20
= 100
(b)
Percent of the pencils left unsold = 100% - 50% = 50% 50% of the pencils that were sold = 5 u 50% of the pencils that were left unsold = 5 u Percent of the pencils left unsold that were black = 70%
Percent of the pencils left unsold that were green = 100% - 70% = 30%
Number of the pencils left unsold that were green
= 30% x 5 u
=
30100 x 5 u
= 1.5 u
Number of green pencils that Michael had at first
= 1.5 u + 2 u
= 3.5 u
= 3.5 x 20
= 70
Answer(s): (a) 100; (b) 70
