Question 1203281
a) find the number of ways the word HISTORY can be arranged.<pre>7! = 5040
ways</pre>b) Find the number of ways the word HISTORY can be arranged if the
letters O and R are 
(i) together,<pre>There are 

1.  6 things: H, I, S, T, OR, Y to arrange in 6! = 720 ways

Plus

2.  6 things: H, I, S, T, RO, Y to arrange in 6! = 720 ways

for a total of 1440 ways.</pre>(il) not together<pre>(Number of arrangements of HISTORY) - (number of arrangements O and R are together.)  

That's

5040 - 1440 = 3600 ways.

Edwin</pre>