Suppose we have 12 books. How many ways are there to put four of them on a shelf?
PLS HELP ME

1) first book can be at any of 4 places

2) Second book can be on any of leftover 3 places

3) Similarly third book on 2 and forth on 1 place

total : 4 * 3*2 * 1 = 24 ways .

other way we have formula 4!/1! =24 , here ordering is important

It is called arrangement or permutations, while if you need to group some objects it is called combination and there we need to consider unique groups only.

example if you need to choose 2 friends for a party out of 4 friends ,

answer will be 4!/2!*2! = 6 groups. (Ordering doesn’t matter hence division)

hope it hleps

PLEASE MARK BRAINLIEST

the expression (1.26)2t reveals the approximate rate of increases in the number of plants semiannually.

hope this : )