PSLE Ian had green pens and black pens for sale. He sold 30 green pens. 70% of the pens sold were black.
- How many green pens and black pens did Ian sell altogether?
- He sold 50% of his pens. 75% of the pens left unsold were green. How many black pens did Ian have at first?
| |
Green |
Black |
Total |
Total in percent |
| Before |
10.5 u |
9.5 u |
20 u |
100% |
| Change |
- 30%
- 3 u |
- 70%
- 7 u |
- 100%
- 10 u |
- 50% |
| After |
75%
7.5 u |
25%
2.5 u |
100%
10 u |
50%
|
70% =
70100 =
710 Total number of pens sold = 10 u
Number of black pens sold = 7 u
Number of green pens sold
= 10 u - 7 u
= 3 u
3 u = 30
1 u = 30 ÷ 3 = 10
Total number of pens sold
= 10 u
= 10 x 10
= 100
(b)
Percent of the pens left unsold = 100% - 50% = 50% 50% of the pens that were sold = 10 u 50% of the pens that were left unsold = 10 u Percent of the pens left unsold that were green = 75%
Percent of the pens left unsold that were black = 100% - 75% = 25%
Number of the pens left unsold that were black
= 25% x 10 u
=
25100 x 10 u
= 2.5 u
Number of black pens that Ian had at first
= 2.5 u + 7 u
= 9.5 u
= 9.5 x 10
= 95
Answer(s): (a) 100; (b) 95
