How many signals can be made using 6 different coloured flags when any number of them can be hoisted at a time?
Given that any number of flags can be hoisted at a time. Hence we need to find out number of signals that can be made using 1 flag, 2 flags, 3 flags, 4 flags, 5 flags and 6 flags and then add all these.
Number of signals that can be made using 1 flag
= $^6P_{1}$ =6
Number of signals that can be made using 2 flags
=$ ^6P_{2} $
=6×5=30
Number of signals that can be made using 3 flags
=$ ^6P_{3}$
=6×5×4=120
Number of signals that can be made using 4 flags
=$ ^6P_{4} $
=6×5×4×3=360
Number of signals that can be made using 5 flags
= $^6P_{5}$
=6×5×4×3×2=720
Number of signals that can be made using 6 flags
= $^6P_{6 }$
=6×5×4×3×2×1=720
Therefore, required number of signals
=6+30+120+360+720+720=1956