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From a box of 10 lightbulbs, you are to remove 4. How many d

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Carcass

Verbal Expert

Joined: 18 Apr 2015

Posts: 15667

GRE 1: Q160 V160

From a box of 10 lightbulbs, you are to remove 4. How many d [#permalink]

30 May 2019, 11:24

Expert Reply

From a box of 10 lightbulbs, you are to remove 4. How many different sets of 4 lightbulbs could you remove?

Show: :: OA

210

Math Review
Question: 9
Page: 297
Difficulty: medium

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GreenlightTestPrep

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Joined: 10 Apr 2015

Posts: 4395

Re: From a box of 10 lightbulbs, you are to remove 4. How many d [#permalink]

31 May 2019, 05:07

Expert Reply

Carcass wrote:

From a box of 10 lightbulbs, you are to remove 4. How many different sets of 4 lightbulbs could you remove?

Show: :: OA

210

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
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