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27 Dec 2017, 01:10
00:00

Difficulty:

15% (low)

Question Stats:

93% (00:50) correct 7% (01:17) wrong based on 43 sessions

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On 3 sales Tom has received commissions of $250,$95, and $175, and has two additional sales pending. If Tom is to receive an average (arithmetic mean) commission of exactly$150 on the 5 sales, then the average (arithmetic mean) of the final two sales must be

A. 60
B. 80
C. 115
D. 230
E. 280

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Re: On 3 sales Tom has received commissions of $250,$95, and $175, and ha [#permalink] ### Show Tags 27 Dec 2017, 01:58 Bunuel wrote: On 3 sales Tom has received commissions of$250, $95, and$175, and has two additional sales pending. If Tom is to receive an average (arithmetic mean) commission of exactly $150 on the 5 sales, then the average (arithmetic mean) of the final two sales must be A. 60 B. 80 C. 115 D. 230 E. 280 We'll take a shortcut to calculation based on properties of the average. This is a Logical approach. Our target is to find two numbers that combine with$250, $95,$175 to give an average of $150. These three numbers have a difference of 100, -55, 25 from 150 for a combined difference of 100-55+25=70. So our remaining two numbers need to compensate for this with -70, which is -70/2 = -35 each. Therefore they must have an average of 150 - 35 = 115. (C) is our answer. Note that the calculations here involve much smaller numbers than $$\frac{(150*5 - (250+175+95))}{2}$$ which is the straightforward, Precise, approach. _________________ David Senior tutor at examPAL Signup for a free GMAT course We won some awards: Join our next webinar (free) Save up to$250 on examPAL packages (special for GMAT Club members)

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### Show Tags

28 Dec 2017, 03:33
Bunuel wrote:
On 3 sales Tom has received commissions of $250,$95, and $175, and has two additional sales pending. If Tom is to receive an average (arithmetic mean) commission of exactly$150 on the 5 sales, then the average (arithmetic mean) of the final two sales must be

A. 60
B. 80
C. 115
D. 230
E. 280

$$Average=\frac{Total.Sales}{Number.Sales}$$, and 2 more sales = $$2x$$

So $$150=\frac{(250+95+175+2x)}{5}$$, $$150(5)=(520+2x)$$, $$x=\frac{750-520}{2}=115$$