How many arrangements of the digits 1, 2, 3, 4, and 5 are there, such that 2 and 4 are not adjacent?
Total number of arrangements = 5!sud21 wrote:How many arrangements of the digits 1, 2, 3, 4, and 5 are there, such that 2 and 4 are not adjacent?
Let us assume that 24 is a sigle element
Number of arrangements of 1, 24,3,5 = 4!
Nuumber of arrangemtns of 1, 42,3,5 = 4!
Number of arrangements such that 2,4 are not adjacent = 5! - 2*4! = 120 - 48 = 72
