PSLE Luke had gold files and black files for sale. He sold 770 gold files. 30% of the files sold were black.
- How many gold files and black files did Luke sell altogether?
- He sold 50% of his files. 70% of the files left unsold were gold. How many black files did Luke have at first?
| |
Gold |
Black |
Total |
Total in percent |
| Before |
14 u |
6 u |
20 u |
100% |
| Change |
- 70%
- 7 u |
- 30%
- 3 u |
- 100%
- 10 u |
- 50% |
| After |
70%
7 u |
30%
3 u |
100%
10 u |
50%
|
30% =
30100 =
310 Total number of files sold = 10 u
Number of black files sold = 3 u
Number of gold files sold
= 10 u - 3 u
= 7 u
7 u = 770
1 u = 770 ÷ 7 = 110
Total number of files sold
= 10 u
= 10 x 110
= 1100
(b)
Percent of the files left unsold = 100% - 50% = 50% 50% of the files that were sold = 10 u 50% of the files that were left unsold = 10 u Percent of the files left unsold that were gold = 70%
Percent of the files left unsold that were black = 100% - 70% = 30%
Number of the files left unsold that were black
= 30% x 10 u
=
30100 x 10 u
= 3 u
Number of black files that Luke had at first
= 3 u + 3 u
= 6 u
= 6 x 110
= 660
Answer(s): (a) 1100; (b) 660
