2 votes 2 votes I am solving with Pigeon Hole Principle. Please correct me if I am wrong. Considering the required number of books as pigeons, days of the month as pigeonholes with 3 pigeons per day. if my approach is wrong, please correct me Combinatory combinatory counting discrete-mathematics + – AnilGoudar asked Jan 11, 2018 AnilGoudar 433 views answer comment Share Follow See all 5 Comments See all 5 5 Comments reply Ajay Jadhav commented Jan 11, 2018 reply Follow Share I think no of holes are poems in set of 3 ,k+1=3 ,k=2 And assuming no of days in month as 30,kn+1=61 poems are necessary 0 votes 0 votes AnilGoudar commented Jan 11, 2018 reply Follow Share will it be 61? 0 votes 0 votes Mk Utkarsh commented Jan 11, 2018 reply Follow Share month can be of 30 or 31 days , 7 poems can keep her busy for 35 days :P to create different sets of 3 we need to choose 3 poems out of 7 poems 7C3 = 35 1 votes 1 votes AnilGoudar commented Jan 11, 2018 reply Follow Share @Mk Utkarsh, Can you please explain this statement? 7 poems can keep her busy for 35 days :P 0 votes 0 votes Mk Utkarsh commented Jan 11, 2018 reply Follow Share the book contain 7 distinct poems and she needs distinct set of 3 poems every day to choose 1st poem she has 7 options to choose 2nd poem she has 6 options to choose 3rd poem she has 5 options but these are permutations so we need to divide by 3! because we don't care about the order. $\frac{7 * 6 * 5}{3 * 2}$ = 35 that means we have 35 distinct set of 3 poems from 7 distinct poems 3 votes 3 votes Please log in or register to add a comment.