PSLE Henry had gold pens and black pens for sale. He sold 330 gold pens. 40% of the pens sold were black.
- How many gold pens and black pens did Henry sell altogether?
- He sold 50% of his pens. 80% of the pens left unsold were gold. How many black pens did Henry have at first?
| |
Gold |
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 pens sold = 5 u
Number of black pens sold = 2 u
Number of gold pens sold
= 5 u - 2 u
= 3 u
3 u = 330
1 u = 330 ÷ 3 = 110
Total number of pens sold
= 5 u
= 5 x 110
= 550
(b)
Percent of the pens left unsold = 100% - 50% = 50% 50% of the pens that were sold = 5 u 50% of the pens that were left unsold = 5 u Percent of the pens left unsold that were gold = 80%
Percent of the pens left unsold that were black = 100% - 80% = 20%
Number of the pens left unsold that were black
= 20% x 5 u
=
20100 x 5 u
= 1 u
Number of black pens that Henry had at first
= 1 u + 2 u
= 3 u
= 3 x 110
= 330
Answer(s): (a) 550; (b) 330
