# Combinatorics - examples - page 12

1. Cancel fractions
Compress the expression of factorial: (n+6)!/(n+4)!-n!/(n-2)!
2. Inverted nine
In the hotel,, Inverted nine" each hotel room number is divisible by 6. How many rooms we can count with three-digit number registered by digits 1,8,7,4,9?
3. To improve
To improve her handwriting Paula practices writing the numbers 1 to 200 in words. How many times will she have written the word "one" in all?
4. How many 2
How many three lettered words can be formed from letters A B C D E G H if repeats are: a) not allowed b) allowed
5. Combinations 7
A multi-course meal has 3 choices. 3 appetizers, 4 main courses, and 3 desserts. How many different combinations to choose from?
6. Find the 2
Find the term independent of x in the expansion of (4x3+1/2x)8
7. Blocks
There are 9 interactive basic building blocks of an organization. How many two-blocks combinations are there?
8. Mumbai
A job placement agency in Mumbai had to send ten students to five companies two to each. Two of the companies are in Mumbai and others are outside. Two of the students prefer to work in Mumbai while three prefer to work outside. In how many ways assignment
9. Election 4
In a certain election there are 3 candidates for president 5 for secretory and 2 for tresurer. Find how many ways the election may (turn out/held).
10. A student
A student is to answer 8 out of 10 questions on the exam. a) find the number n of ways the student can choose 8 out of 10 questions b) find n if the student must answer the first three questions c) How many if he must answer at least 4 of the first 5 que
11. Normal distribution GPA
The average GPA is 2.78 with a standard deviation of 4.5. What are students in the bottom the 20% having what GPA?
12. Component fail
There is a 90 percent chance that a particular type of component will perform adequately under high temperature conditions. If the device involved has four such components, determine the probability that the device is inoperable because exactly one of the.

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