In this case, the order in which we select the 4 bulbs does not matter.
For example, selecting bulb A, then bulb D, then bulb E, and then bulb H, is the SAME as selecting bulb H, then bulb D, then bulb A, and then bulb E
So, we can use COMBINATIONS.

We can select 4 bulbs from 10 bulbs in 10C4 ways

10C4 = (10)(9)(8)(7)/(4)(3)(2)(1) = 210

Answer: 210

Cheers,
Brent
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Brent Hanneson – Creator of greenlighttestprep.com
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