PSLE Ivan had yellow pens and red pens for sale. He sold 210 yellow pens. 70% of the pens sold were red.
- How many yellow pens and red pens did Ivan sell altogether?
- He sold 50% of his pens. 80% of the pens left unsold were yellow. How many red pens did Ivan have at first?
| |
Yellow |
Red |
Total |
Total in percent |
| Before |
11 u |
9 u |
20 u |
100% |
| Change |
- 30%
- 3 u |
- 70%
- 7 u |
- 100%
- 10 u |
- 50% |
| After |
80%
8 u |
20%
2 u |
100%
10 u |
50%
|
70% =
70100 =
710 Total number of pens sold = 10 u
Number of red pens sold = 7 u
Number of yellow pens sold
= 10 u - 7 u
= 3 u
3 u = 210
1 u = 210 ÷ 3 = 70
Total number of pens sold
= 10 u
= 10 x 70
= 700
(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 yellow = 80%
Percent of the pens left unsold that were red = 100% - 80% = 20%
Number of the pens left unsold that were red
= 20% x 10 u
=
20100 x 10 u
= 2 u
Number of red pens that Ivan had at first
= 2 u + 7 u
= 9 u
= 9 x 70
= 630
Answer(s): (a) 700; (b) 630
