Answer:
Number of story books bought = 100
C.P. of each book = Rs. 135
C.P. of all 100 books = Rs. (135×100)= Rs. 13500
C.P. of 90 books = Rs. (135×90)= Rs. 12150
Number of books donated = 10
Number of books sold = 100-10=90
Loss% in the transaction = 2%
S.P. of all books = (C.P./100)(100-loss%)
=Rs. (12150/100×98)
Thus, S.P. of each book
= Rs. {(12150/100×98)÷90}
= Rs. (12150/100×98/90)
= Rs. 132.3