Question

The number of ways of selecting 8 books from a
library which has 9 identical books each on
Mathematics, Physics, Chemistry and English is
(plz Answer with explaination)​

Answer 1

your question is quite good. now we will denote maths equals to M physics equals to p chemistry equals to see English equal to now as each books of subject is identical hence the number of ways to select one book auto books are 8 books of a particular subject will be one as there is no for distinction hence any combination is passport is to all 9 books can be of English are no books can be off in the selected books and so on .hence,

all are identical so total number of ways can be calculated by formula

number of maths with = X 1

numberPhysics books =X 2

number of chemistry books = x 3

number of English books = x1+x2+x3+x4=8

= 8 +4-1 c4- 1= 8 = 11 C3

= 165

maths books =165

Physics books = 166

chemistry = 167

English books= 168

i think the answer is correct