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Four flags of different colours are available. A signal uses at least 2 of them hoisted one above another. How many signals can be made?

Competition practicePermutations & Combinations

A64
B48
C60
D24

Step-by-Step Solution

2 flags:

^{4} P_{2} = 12

; 3 flags:

^{4} P_{3} = 24

; 4 flags:

^{4} P_{4} = 24

. Total

12 + 24 + 24 = 60

. (24 uses only all four.)

Answer: C) 60

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