PSLE Peter had blue files and black files for sale. He sold 40 blue files. 60% of the files sold were black.
- How many blue files and black files did Peter sell altogether?
- He sold 50% of his files. 60% of the files left unsold were blue. How many black files did Peter have at first?
| |
Blue |
Black |
Total |
Total in percent |
| Before |
5 u |
5 u |
10 u |
100% |
| Change |
- 40%
- 2 u |
- 60%
- 3 u |
- 100%
- 5 u |
- 50% |
| After |
60%
3 u |
40%
2 u |
100%
5 u |
50%
|
60% =
60100 =
35 Total number of files sold = 5 u
Number of black files sold = 3 u
Number of blue files sold
= 5 u - 3 u
= 2 u
2 u = 40
1 u = 40 ÷ 2 = 20
Total number of files sold
= 5 u
= 5 x 20
= 100
(b)
Percent of the files left unsold = 100% - 50% = 50% 50% of the files that were sold = 5 u 50% of the files that were left unsold = 5 u Percent of the files left unsold that were blue = 60%
Percent of the files left unsold that were black = 100% - 60% = 40%
Number of the files left unsold that were black
= 40% x 5 u
=
40100 x 5 u
= 2 u
Number of black files that Peter had at first
= 2 u + 3 u
= 5 u
= 5 x 20
= 100
Answer(s): (a) 100; (b) 100
