PSLE Pierre had black pens and green pens for sale. He sold 770 black pens. 30% of the pens sold were green.
- How many black pens and green pens did Pierre sell altogether?
- He sold 50% of his pens. 60% of the pens left unsold were black. How many green pens did Pierre have at first?
| |
Black |
Green |
Total |
Total in percent |
| Before |
13 u |
7 u |
20 u |
100% |
| Change |
- 70%
- 7 u |
- 30%
- 3 u |
- 100%
- 10 u |
- 50% |
| After |
60%
6 u |
40%
4 u |
100%
10 u |
50%
|
30% =
30100 =
310 Total number of pens sold = 10 u
Number of green pens sold = 3 u
Number of black pens sold
= 10 u - 3 u
= 7 u
7 u = 770
1 u = 770 ÷ 7 = 110
Total number of pens sold
= 10 u
= 10 x 110
= 1100
(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 black = 60%
Percent of the pens left unsold that were green = 100% - 60% = 40%
Number of the pens left unsold that were green
= 40% x 10 u
=
40100 x 10 u
= 4 u
Number of green pens that Pierre had at first
= 4 u + 3 u
= 7 u
= 7 x 110
= 770
Answer(s): (a) 1100; (b) 770
