PSLE Ben had black pens and green pens for sale. He sold 240 black pens. 70% of the pens sold were green.
- How many black pens and green pens did Ben sell altogether?
- He sold 50% of his pens. 70% of the pens left unsold were black. How many green pens did Ben have at first?
|
Black |
Green |
Total |
Total in percent |
Before |
10 u |
10 u |
20 u |
100% |
Change |
- 30% - 3 u |
- 70% - 7 u |
- 100% - 10 u |
- 50% |
After |
70% 7 u |
30% 3 u |
100% 10 u |
50%
|
70% =
70100 =
710 Total number of pens sold = 10 u
Number of green pens sold = 7 u
Number of black pens sold
= 10 u - 7 u
= 3 u
3 u = 240
1 u = 240 ÷ 3 = 80
Total number of pens sold
= 10 u
= 10 x 80
= 800
(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 = 70%
Percent of the pens left unsold that were green = 100% - 70% = 30%
Number of the pens left unsold that were green
= 30% x 10 u
=
30100 x 10 u
= 3 u
Number of green pens that Ben had at first
= 3 u + 7 u
= 10 u
= 10 x 80
= 800
Answer(s): (a) 800; (b) 800