PSLE Justin had silver pens and blue pens for sale. He sold 240 silver pens. 40% of the pens sold were blue.
- How many silver pens and blue pens did Justin sell altogether?
- He sold 50% of his pens. 80% of the pens left unsold were silver. How many blue pens did Justin have at first?
| |
Silver |
Blue |
Total |
Total in percent |
| Before |
7 u |
3 u |
10 u |
100% |
| Change |
- 60%
- 3 u |
- 40%
- 2 u |
- 100%
- 5 u |
- 50% |
| After |
80%
4 u |
20%
1 u |
100%
5 u |
50%
|
40% =
40100 =
25 Total number of pens sold = 5 u
Number of blue pens sold = 2 u
Number of silver pens sold
= 5 u - 2 u
= 3 u
3 u = 240
1 u = 240 ÷ 3 = 80
Total number of pens sold
= 5 u
= 5 x 80
= 400
(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 silver = 80%
Percent of the pens left unsold that were blue = 100% - 80% = 20%
Number of the pens left unsold that were blue
= 20% x 5 u
=
20100 x 5 u
= 1 u
Number of blue pens that Justin had at first
= 1 u + 2 u
= 3 u
= 3 x 80
= 240
Answer(s): (a) 400; (b) 240
