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?	Select the correct option.
A) 10 B) 12 C) 20 D) 24 E) 36
Consider a flagpole with 3 vertical slots for flags   As we have to select different flags we can do as follows   topmost flag can be paced in 4 ways   middle flag can be placed in 3 ways   bottom most flag can be placed in 2 ways   (order doesn't matter the selection matters)   Total ways = 4 * 3 * 2= 
<gadget id="calculator">4 * 3 * 2</gadget>
<output>24</output>
24 ways   correct answer - 24
<result>D</result>
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?