PSLE Mark had blue pens and black pens for sale. He sold 180 blue pens. 40% of the pens sold were black.
- How many blue pens and black pens did Mark sell altogether?
- He sold 50% of his pens. 75% of the pens left unsold were blue. How many black pens did Mark have at first?
| |
Blue |
Black |
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 black pens sold = 2 u
Number of blue pens sold
= 5 u - 2 u
= 3 u
3 u = 180
1 u = 180 ÷ 3 = 60
Total number of pens sold
= 5 u
= 5 x 60
= 300
(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 blue = 75%
Percent of the pens left unsold that were black = 100% - 75% = 25%
Number of the pens left unsold that were black
= 25% x 5 u
=
25100 x 5 u
= 1.25 u
Number of black pens that Mark had at first
= 1.25 u + 2 u
= 3.25 u
= 3.25 x 60
= 195
Answer(s): (a) 300; (b) 195
