PSLE Albert had green files and black files for sale. He sold 770 green files. 30% of the files sold were black.
- How many green files and black files did Albert sell altogether?
- He sold 50% of his files. 75% of the files left unsold were green. How many black files did Albert have at first?
| |
Green |
Black |
Total |
Total in percent |
| Before |
14.5 u |
5.5 u |
20 u |
100% |
| Change |
- 70%
- 7 u |
- 30%
- 3 u |
- 100%
- 10 u |
- 50% |
| After |
75%
7.5 u |
25%
2.5 u |
100%
10 u |
50%
|
30% =
30100 =
310 Total number of files sold = 10 u
Number of black files sold = 3 u
Number of green 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 green = 75%
Percent of the files left unsold that were black = 100% - 75% = 25%
Number of the files left unsold that were black
= 25% x 10 u
=
25100 x 10 u
= 2.5 u
Number of black files that Albert had at first
= 2.5 u + 3 u
= 5.5 u
= 5.5 x 110
= 605
Answer(s): (a) 1100; (b) 605
