Answer: Fernando has 29 books
Step-by-step explanation:
The prime numbers between 21 and 30 are 23 and 29.
hence, the possible number of books Fernando has 23 or 29.
After taking 4 books away, the total number of books left can be :-
23-4=19
Since, 19 is not a square number so he cannot be able to place the same number of books on each shelf of his bookcase.
So Fernado doesn't have 23 books.
29-4=25
Also, [tex]5^2=25[/tex]
Here, 25 is a square number so he will be able to place the same number of books on each shelf of his bookcase.
Therefore, Fernando has 29 books.
