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A 36 year old employee joined a law firm and as a result the average

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V
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A 36 year old employee joined a law firm and as a result the average [#permalink]

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New post 08 Jan 2018, 06:26
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Question Stats:

55% (00:37) correct 45% (00:35) wrong based on 19 sessions

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A 36 year old employee joined a law firm and as a result the average (arithmetic mean) age jumped from 30 to 32. How many employees are currently employed in the firm?

A. 2
B. 3
C. 4
D. 5
E. 6
[Reveal] Spoiler: OA

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Re: A 36 year old employee joined a law firm and as a result the average [#permalink]

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New post 08 Jan 2018, 09:59
Bunuel wrote:
A 36 year old employee joined a law firm and as a result the average (arithmetic mean) age jumped from 30 to 32. How many employees are currently employed in the firm?

A. 2
B. 3
C. 4
D. 5
E. 6


Lets say before joining of this employee, there were 'n' people in the firm. So their total age = Average*n = 30*n

Now there is an addition of a person whose age is 36. Now, new total age = 30*n + 36, and new number of people = 'n+1'.
So new average = (30n + 36)/(n+1) and this is given to be 32. So 30n + 36 = 32(n+1). Solving this we get n=2.

That means earlier, there were 2 people in the firm, thus now (after this new person has joined) there are 3 people in the firm.

Hence B answer
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Re: A 36 year old employee joined a law firm and as a result the average [#permalink]

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New post 08 Jan 2018, 10:18
Bunuel wrote:
A 36 year old employee joined a law firm and as a result the average (arithmetic mean) age jumped from 30 to 32. How many employees are currently employed in the firm?

A. 2
B. 3
C. 4
D. 5
E. 6


\(30n + 36 = 32 ( n + 1)\)

Or, \(30n + 36 = 32n + 32\)

Or, \(2n = 4\)

So, \(n = 2\)

After joining of a new employee total number of employees will be 3 , answer will be (B)
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Re: A 36 year old employee joined a law firm and as a result the average   [#permalink] 08 Jan 2018, 10:18
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