PSLE Fabian had black pens and red pens for sale. He sold 180 black pens. 70% of the pens sold were red.
- How many black pens and red pens did Fabian sell altogether?
- He sold 50% of his pens. 60% of the pens left unsold were black. How many red pens did Fabian have at first?
|
Black |
Red |
Total |
Total in percent |
Before |
9 u |
11 u |
20 u |
100% |
Change |
- 30% - 3 u |
- 70% - 7 u |
- 100% - 10 u |
- 50% |
After |
60% 6 u |
40% 4 u |
100% 10 u |
50%
|
70% =
70100 =
710 Total number of pens sold = 10 u
Number of red pens sold = 7 u
Number of black pens sold
= 10 u - 7 u
= 3 u
3 u = 180
1 u = 180 ÷ 3 = 60
Total number of pens sold
= 10 u
= 10 x 60
= 600
(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 red = 100% - 60% = 40%
Number of the pens left unsold that were red
= 40% x 10 u
=
40100 x 10 u
= 4 u
Number of red pens that Fabian had at first
= 4 u + 7 u
= 11 u
= 11 x 60
= 660
Answer(s): (a) 600; (b) 660