Averages

naaga wrote:Month Average Price
per Dozen

April $1.26
May $1.20
June $1.08


19. The table above shows the average (arithmetic mean) price per dozen of the large grade A eggs sold in a certain store during three successive months. If as many dozen were sold in April as in May, and twice as many were sold in June as in April, what was the average price per dozen of the eggs sold over the three-month period?

Let x be the number of dozen sold
[1.26x + 1.20x + 1.08(2x)]/[x+x+2x]

[2.46x + 2.16x] / [4x]

[4.62x] / [4x]

x = 1.155 or 1.16

Answer D.

naaga wrote:Month Average Price
per Dozen

April $1.26
May $1.20
June $1.08


19. The table above shows the average (arithmetic mean) price per dozen of the large grade A eggs sold in a certain store during three successive months. If as many dozen were sold in April as in May, and twice as many were sold in June as in April, what was the average price per dozen of the eggs sold over the three-month period?
(A) $1.08
(B) $1.10
(C) $1.14
(D) $1.16
(E) $1.18

Another solution is to use the weighted average formula.

Weighted Average = Wght1*Avg1 + Wght2*Avg2 + Wght3*Avg3 + ...

Here, April and May each have weight 1/4 and June has weight 1/2, so:

Weighted Average = (1/4)(126) + (1/4)(120) + (1/2)(108)
= 31.5 + 30 + 54 (I converted to cents to eliminate decimals)
= 115.5 cents = $1.16 (rounded up)

Note: the question doesn't talk about rounding up or approximation, which leads me to believe that it's not a real GMAT question. The "true" answer to the question asked isn't $1.16, it's $1.155, and the GMAT would either explicitly tell us to round to the nearest cent or would have precise choices.

What's the source?