Question

Definition of permutation, Number of permutations
with or without repetition, Conditional permutations
Ir the best and the worst paper never appear together, then
examination papers can be arranged in how many ways
(a) 120
(b) 180
(0) None of these​

Answer 1

Answer:

A permutation is a mathematical technique that determines the number of possible arrangements in a set when the order of the arrangements matters. ... In other words, the arrangements ab and be in permutations are considered different arrangements, while in combinations, these arrangements are equal.

Permutation can be classified in three different categories:

Permutation of n different objects (when repetition is not allowed)

Repetition, where repetition is allowed.

Permutation when the objects are not distinct (Permutation of multi sets).

The number of permutations of n objects taken r at a time is determined by the following formula: P(n,r)=n! (n−r)! A code have 4 digits in a specific order, the digits are between 0-9.

$P(n,r)=\frac{n!}{(n-r)!}$

Q)

If the best and worst papers appear always together, the number of ways is 5!×2. Therefore, the required number of ways is as follows.

Total number of ways without any restrictions−Number of ways when best and wort paper are together =6!−5!×2=480.

(D)None of these