PSLE Billy had black markers and red markers for sale. He sold 300 black markers. 70% of the markers sold were red.
- How many black markers and red markers did Billy sell altogether?
- He sold 50% of his markers. 80% of the markers left unsold were black. How many red markers did Billy have at first?
| |
Black |
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 markers sold = 10 u
Number of red markers sold = 7 u
Number of black markers sold
= 10 u - 7 u
= 3 u
3 u = 300
1 u = 300 ÷ 3 = 100
Total number of markers sold
= 10 u
= 10 x 100
= 1000
(b)
Percent of the markers left unsold = 100% - 50% = 50% 50% of the markers that were sold = 10 u 50% of the markers that were left unsold = 10 u Percent of the markers left unsold that were black = 80%
Percent of the markers left unsold that were red = 100% - 80% = 20%
Number of the markers left unsold that were red
= 20% x 10 u
=
20100 x 10 u
= 2 u
Number of red markers that Billy had at first
= 2 u + 7 u
= 9 u
= 9 x 100
= 900
Answer(s): (a) 1000; (b) 900
