Permutations Practice Test 2

Question : 17 of 30

Marks: +1, -0

There are 10 lamps in a hall. Each one of them can be switched on independently. The number ofways in which the hall can be illuminated is:

Solution:

Each bulb has two choices, either switched on or off.
∴ Required number

= 2^10 - 1 = 1023

(Since in one way, when all switches are off, the hall will not be illuminated.)

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