PSLE Ethan had red pens and blue pens for sale. He sold 20 red pens. 60% of the pens sold were blue.
- How many red pens and blue pens did Ethan sell altogether?
- He sold 50% of his pens. 60% of the pens left unsold were red. How many blue pens did Ethan have at first?
| |
Red |
Blue |
Total |
Total in percent |
| Before |
5 u |
5 u |
10 u |
100% |
| Change |
- 40%
- 2 u |
- 60%
- 3 u |
- 100%
- 5 u |
- 50% |
| After |
60%
3 u |
40%
2 u |
100%
5 u |
50%
|
60% =
60100 =
35 Total number of pens sold = 5 u
Number of blue pens sold = 3 u
Number of red pens sold
= 5 u - 3 u
= 2 u
2 u = 20
1 u = 20 ÷ 2 = 10
Total number of pens sold
= 5 u
= 5 x 10
= 50
(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 red = 60%
Percent of the pens left unsold that were blue = 100% - 60% = 40%
Number of the pens left unsold that were blue
= 40% x 5 u
=
40100 x 5 u
= 2 u
Number of blue pens that Ethan had at first
= 2 u + 3 u
= 5 u
= 5 x 10
= 50
Answer(s): (a) 50; (b) 50
