In a library, for every three fiction books, there is one non-fiction book. If 10 more non-fiction books are added, the ratio of non-fiction to fiction books becomes 1:2. What is the total number of books in the library after the addition?

(a) 80

(b) 90

(c) 70

(d) 100

Question

In a library, for every three fiction books, there is one non-fiction book. If 10 more non-fiction books are added, the ratio of non-fiction to fiction books becomes 1:2. What is the total number of books in the library after the addition?

(a) 80

(b) 90

(c) 70

(d) 100

ONLiNE UPSC · Accepted Answer

Let the number of non-fiction books be x. 

Since the ratio is 1 non-fiction to 3 fiction books, the number of fiction books is 3x.
After adding 10 more non-fiction books, the new count becomes x+10, and the new ratio is:

(x + 10)/3x = 1/2 

On solving,

We get, x=20 

So, non-fiction = 20, fiction = 60. Total books before addition = 80, after adding 10 = 90.

Hence, option b is correct.

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