Question
How many signals can be given by means of 10 different flags when at a time 4 flags are used, one above the other?
- 10P4
- 10C4
- 4
- 40
Hint:
Use formula
The correct answer is: 10P4
You are given 10 flags of different colors and you can give signals, but use only 4 flags.
First you have to choose 4 flags from 10 flags
This can be done in 
ways
Among this 4 flags of different colors, 4! ways of different arrangements are possible
So total number of signals = 
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