PSLE George had black files and green files for sale. He sold 240 black files. 70% of the files sold were green.
- How many black files and green files did George sell altogether?
- He sold 50% of his files. 75% of the files left unsold were black. How many green files did George have at first?
| |
Black |
Green |
Total |
Total in percent |
| Before |
10.5 u |
9.5 u |
20 u |
100% |
| Change |
- 30%
- 3 u |
- 70%
- 7 u |
- 100%
- 10 u |
- 50% |
| After |
75%
7.5 u |
25%
2.5 u |
100%
10 u |
50%
|
70% =
70100 =
710 Total number of files sold = 10 u
Number of green files sold = 7 u
Number of black files sold
= 10 u - 7 u
= 3 u
3 u = 240
1 u = 240 ÷ 3 = 80
Total number of files sold
= 10 u
= 10 x 80
= 800
(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 black = 75%
Percent of the files left unsold that were green = 100% - 75% = 25%
Number of the files left unsold that were green
= 25% x 10 u
=
25100 x 10 u
= 2.5 u
Number of green files that George had at first
= 2.5 u + 7 u
= 9.5 u
= 9.5 x 80
= 760
Answer(s): (a) 800; (b) 760
