Question

Fernando has a prime number of books between 21 30. He says that if he takes 4 of the books away, he will be able to place the same number of books on each shelf of his bookcase. How many books does Fernando have?

Answer 1

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, $5^2=25$

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.