There were some grey, brown and black files in a box.
211 of the files were brown. The ratio of the number of grey files to the number of black files was 4 : 5. There were 315 fewer brown files than black files.
- Find the ratio of the number of grey files to the number of brown files to the number of black files in the box.
- How many black files were there?
Brown |
Grey |
Black |
Total |
2 |
9 |
11 |
|
4 |
5 |
|
2 u |
4 u |
5 u |
11 u |
(a)
Grey : Brown : Black
4 : 2 : 5
(b)
Number of fewer brown files than black files
= 5 u - 2 u
= 3 u
3 u = 315
1 u = 315 ÷ 3 = 105
Number of black files
= 5 u
= 5 x 105
= 525
Answer(s): (a) 4 : 2 : 5; (b) 525