A librarian purchased 50 story–books for his library. But he saw that he could get14 more books by spending Rs. 76 more and the average price per book would be reduced by Re. 1. The average price (in Rs.) of each book he bought, was :

Let the average cost of each book bought (of 64 books) be Rs. x.

According to the question, 64 × x–50(x + 1)=76

$\Rightarrow \quad 64 x-50 x-50=76$

$\Rightarrow \quad 14 x=76+50=126$

$\Rightarrow \quad x=\frac{126}{14}=9$

$\therefore$ Required average price $=9+1=$ Rs. 10