PSLE Oscar had black pens and red pens for sale. He sold 300 black pens. 40% of the pens sold were red.
- How many black pens and red pens did Oscar sell altogether?
- He sold 50% of his pens. 75% of the pens left unsold were black. How many red pens did Oscar have at first?
| |
Black |
Red |
Total |
Total in percent |
| Before |
6.75 u |
3.25 u |
10 u |
100% |
| Change |
- 60%
- 3 u |
- 40%
- 2 u |
- 100%
- 5 u |
- 50% |
| After |
75%
3.75 u |
25%
1.25 u |
100%
5 u |
50%
|
40% =
40100 =
25 Total number of pens sold = 5 u
Number of red pens sold = 2 u
Number of black pens sold
= 5 u - 2 u
= 3 u
3 u = 300
1 u = 300 ÷ 3 = 100
Total number of pens sold
= 5 u
= 5 x 100
= 500
(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 black = 75%
Percent of the pens left unsold that were red = 100% - 75% = 25%
Number of the pens left unsold that were red
= 25% x 5 u
=
25100 x 5 u
= 1.25 u
Number of red pens that Oscar had at first
= 1.25 u + 2 u
= 3.25 u
= 3.25 x 100
= 325
Answer(s): (a) 500; (b) 325
