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by anjaligeorge1 » Wed Jan 07, 2009 1:34 pm
Each signal that a certain ship can make is comprised of 3 different flags hanging
vertically in a particular order. How many unique signals can be made by using 4
different flags?
A. 10
B. 12
C. 20
D. 24
E. 36
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by DavoodBeater » Wed Jan 07, 2009 1:59 pm
4*3*2=24

to easier understand, consider numbers such as 1,2,3 and 4.
how many 3digits number can you make with these numbers?
first you have 4 choices, then 3 and the 2.
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by nervesofsteel » Thu Jan 08, 2009 12:03 am
D 24

Choose and 3 flags out of 4

4C3
arrange them in any order = 3 !

so and = 4C3 * 3!

24
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by welcome » Thu Jan 08, 2009 6:23 am
Permutation comes when ORDER matters.

Choosing 3 out of 4 will be 4P3 = 4!/(4-3)! = 24. Ans-D.
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