PSLE Harry had black pencils and yellow pencils for sale. He sold 240 black pencils. 40% of the pencils sold were yellow.
- How many black pencils and yellow pencils did Harry sell altogether?
- He sold 50% of his pencils. 60% of the pencils left unsold were black. How many yellow pencils did Harry have at first?
| |
Black |
Yellow |
Total |
Total in percent |
| Before |
6 u |
4 u |
10 u |
100% |
| Change |
- 60%
- 3 u |
- 40%
- 2 u |
- 100%
- 5 u |
- 50% |
| After |
60%
3 u |
40%
2 u |
100%
5 u |
50%
|
40% =
40100 =
25 Total number of pencils sold = 5 u
Number of yellow pencils sold = 2 u
Number of black pencils sold
= 5 u - 2 u
= 3 u
3 u = 240
1 u = 240 ÷ 3 = 80
Total number of pencils sold
= 5 u
= 5 x 80
= 400
(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 = 60%
Percent of the pencils left unsold that were yellow = 100% - 60% = 40%
Number of the pencils left unsold that were yellow
= 40% x 5 u
=
40100 x 5 u
= 2 u
Number of yellow pencils that Harry had at first
= 2 u + 2 u
= 4 u
= 4 x 80
= 320
Answer(s): (a) 400; (b) 320
