Answer:
<em>1680 is the answer.</em>
Step-by-step explanation:
Here, we have 11 letters in the word <em>MISSISSIPPI.</em>
Repetition of letters:
M - 1 time
I - 4 times
S - 4 times
P - 2 times
As per question statement, we need a substring MISS in the resultant strings.
So, we need to treat MISS as one unit so that <em>MISS always comes together in all the strings</em>.
The resultant strings will look like:
<em>xxxxMISSxxx</em>
<em>xxMISSxxxxx</em>
<em>and so on.</em>
After we treat <em>MISS </em>as one unit, total letters = 8
Repetition of letters:
MISS - 1 time
I - 3 times
S - 2 times
P - 2 times
The formula for combination of letters with total of <em>n </em>letters:
where <em>p, q</em> and <em>r</em> are the number of times other letters are getting repeated.
<em>p = 3</em>
<em>q = 2</em>
<em>r = 2</em>
<em></em>
So, required number of strings that contain MISS as substring:
So, <em>1680 is the answer.</em>