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प्रश्न
A hall has 12 lamps and every lamp can be switched on independently. Find the number of ways of illuminating the hall.
उत्तर
Every lamp is either ON or OFF.
There are 12 lamps
Number of instances = 212
This number includes the case in which all 12
lamps are OFF.
∴ Required Number = 212 – 1 = 4095
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