Given parameters:
Ratio of organic to non-organic = 2:8
Total number of pages in the book = 400
Unknown:
Number of pages of organic = ?
Number of pages of non-organic = ?
Ratios establishes the proportion of parts in a whole.
We can find the whole from the part and likewise the part from the whole if we know the ratio;
To solve this problem;
Sum up the ratio ; 2 + 8 = 10
Number of pages of organic =
= 80pages
Number of pages of non-organic =
= 320pages
We need 80 pages of organic and 320 non- organic pages to make up the chemistry book.