There were some grey, brown and black notebooks in a box.
111 of the notebooks were brown. The ratio of the number of grey notebooks to the number of black notebooks was 3 : 7. There were 312 fewer brown notebooks than black notebooks.
- Find the ratio of the number of grey notebooks to the number of brown notebooks to the number of black notebooks in the box.
- How many black notebooks were there?
Brown |
Grey |
Black |
Total |
1 |
10 |
11 |
|
3 |
7 |
|
1 u |
3 u |
7 u |
11 u |
(a)
Grey : Brown : Black
3 : 1 : 7
(b)
Number of fewer brown notebooks than black notebooks
= 7 u - 1 u
= 6 u
6 u = 312
1 u = 312 ÷ 6 = 52
Number of black notebooks
= 7 u
= 7 x 52
= 364
Answer(s): (a) 3 : 1 : 7; (b) 364