- Seven books are placed one above the other in a particualr way.
- History book is placed exactly above Civics book.
- Geography book is fourth from the bottom and English book is fifth from the top.
- There are two books in between Civics and Economics books.
How many books are there between Civics and Science books ?
To answer this question, which other extra information is required, if any, from the following ?
Clearly, the sequence of the five books mentioned, from top to bottom is :
---, History, Civics, Geography, English, Economics, ----
Clearly, (c) gives us the clue that Science book is placed at the bottom.
Thus, we know that there are three books between Civics and Science.