Carcass wrote:
From a box of 10 lightbulbs, you are to remove 4. How many different sets of 4 lightbulbs could you remove?
Math Review
Question: 9
Page: 297
Difficulty: medium
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
_________________
Brent Hanneson – Creator of greenlighttestprep.com
Sign up for my free GRE Question of the Day emails
close
