PSLE Caden had green pencils and black pencils for sale. He sold 360 green pencils. 40% of the pencils sold were black.
- How many green pencils and black pencils did Caden sell altogether?
- He sold 50% of his pencils. 80% of the pencils left unsold were green. How many black pencils did Caden have at first?
| |
Green |
Black |
Total |
Total in percent |
| Before |
7 u |
3 u |
10 u |
100% |
| Change |
- 60%
- 3 u |
- 40%
- 2 u |
- 100%
- 5 u |
- 50% |
| After |
80%
4 u |
20%
1 u |
100%
5 u |
50%
|
40% =
40100 =
25 Total number of pencils sold = 5 u
Number of black pencils sold = 2 u
Number of green pencils sold
= 5 u - 2 u
= 3 u
3 u = 360
1 u = 360 ÷ 3 = 120
Total number of pencils sold
= 5 u
= 5 x 120
= 600
(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 green = 80%
Percent of the pencils left unsold that were black = 100% - 80% = 20%
Number of the pencils left unsold that were black
= 20% x 5 u
=
20100 x 5 u
= 1 u
Number of black pencils that Caden had at first
= 1 u + 2 u
= 3 u
= 3 x 120
= 360
Answer(s): (a) 600; (b) 360
