Let number of ways of different selections of $6$ books can be made from $11$ different books such that
$(i)$ Two particular books are always selected be k
$(i i)$ Two particular books are never selected be m
Find $(k - m) / 7 ?$

Open in App

Solution

$(i) k =^{11 - 2} C_{6 - 2} =^{9} C_{4} = 126$
$(i i) m =^{11 - 2} C_{6} =^{9} C_{6} = 84$
Thus $(k - m) / 7 = 42 / 7 = 6$

Suggest Corrections

Similar questions

Q. How many different selections of 4 books can be made from 10 different books, if
(i) there is no restriction;
(ii) two particular books are always selected;
(iii) two particular books are never selected?

Q. How many different selections of 6 books can be made from 10 different books?

Q. There are

100

different books in a shelf. Number of ways in which

3

books can be selected so that no two of which are neighbours is?

Q. There are

10

different books in a shelf. Find the number of ways in which

3

books can be selected so that exactly two of them are consecutive.

In how many ways can 7 different books be arranged in a shelf? In how many ways can we arrange three particulars books so that they are always together?

Join BYJU'S Learning Program

Let number of ways of different selections of 6 books can be made from 11 different books such that(i) Two particular books are always selected be k(ii) Two particular books are never selected be mFind (k−m)/7?

(i)k=11−2C6−2=9C4=126(ii)m=11−2C6=9C6=84Thus (k−m)/7=42/7=6

Let number of ways of different selections of $6$ books can be made from $11$ different books such that
$(i)$ Two particular books are always selected be k
$(i i)$ Two particular books are never selected be m
Find $(k - m) / 7 ?$

$(i) k =^{11 - 2} C_{6 - 2} =^{9} C_{4} = 126$
$(i i) m =^{11 - 2} C_{6} =^{9} C_{6} = 84$
Thus $(k - m) / 7 = 42 / 7 = 6$