In how many ways can the letters of the word 'ARRANGE' be arranged? How many of these arrangements are in which (1) two R's come togethe
Question
In how many ways can the letters of the word 'ARRANGE' be arranged?
How many of these arrangements are in which (1) two R's come together?
Solution
Sure, I can help with that.
First, let's find out how many ways the letters of the word 'ARRANGE' can be arranged.
The word 'ARRANGE' has 7 letters, but the letters 'A', 'R' and 'N' are repeated.
The formula for permutations of a multiset (where some items are repeated) is n! / (r1! * r2! * ... * rk!), where n is the total number of items, and r1, r2, ..., rk are the numbers of each type of item.
In this case, n = 7 (the total number of letters), r1 = 2 (the number of 'A's), r2 = 2 (the number of 'R's), and r3 = 2 (the number of 'N's).
So the total number of arrangements is 7! / (2! * 2! * 2!) = 2,520.
Now, let's find out how many of these arrangements have the two 'R's together.
If we consider the two 'R's as a single item, then we have 6 items to arrange ('A', 'A', 'N', 'N', 'G', 'E', and 'RR').
So the total number of arrangements is 6! / (2! * 2!) = 360.
But, the 'RR' can be arranged in 2! = 2 ways.
So the total number of arrangements where the two 'R's are together is 360 * 2 = 720.
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