A merchant paid $300 for a shipment of x identical calculators. The merchant used 2 of the calculators as demonstrators and sold each of the others for $5 more than the average (arithmetic mean) cost of the x calculators. If the total revenue from the sale of the calculators was $120 more than the cost of the shipment, how many calculators were in the shipment?
A. 24
B. 25
C. 26
D. 28
E. 30
Is there a strategic approach to this question?
OA: E
A merchant paid $300 for a shipment of x identical calculato
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Here's one approach:ardz24 wrote:A merchant paid $300 for a shipment of x identical calculators. The merchant used 2 of the calculators as demonstrators and sold each of the others for $5 more than the average (arithmetic mean) cost of the x calculators. If the total revenue from the sale of the calculators was $120 more than the cost of the shipment, how many calculators were in the shipment?
A. 24
B. 25
C. 26
D. 28
E. 30
If it costs $300 to purchase x calculators, then the average cost per calculator is 300/x
Later, the calculators are sold for $5 more than the average purchase cost of 300/x dollars
So, the resell price is 300/x + 5
How many were sold? Well, the merchant began with x calculators, but used 2 as demonstrators, so the merchant sold x - 2 calculators.
Finally, the merchant's profit was $120 (after a $300 investment). So, the revenue was $420
We can now write an equation: (300/x + 5)(x - 2) = 420
IMPORTANT: This is an awful equation to solve. At this point, it may be faster to try plugging in the answer choices.
Or we can solve the equation.
(300/x + 5)(x - 2) = 420
Expand: 300 - (600/x) + 5x - 10 = 420
Multiply both sides by x: 300x - 600 + 5x^2 - 10x = 420x
Simplify: 5x^2 - 130x - 600 = 0
Divide both sides by 5: x^2 - 26x - 120 = 0
Factor: (x - 30)(x + 4) = 0
So, x = 30 or x = -4
Since x can't be negative, x = [spoiler]30 = E[/spoiler]
Cheers,
Brent
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Hi ardz24,
The information in the prompt include a variety of nice 'round' numbers, so it's likely that the number of calculators in the shipment is also a round number AND divides evenly into 300. Only two of the answers 'fit' that idea - 25 and 30, so let's TEST THE ANSWERS and see if either of those values fits all of the information given in the prompt.
IF.... X = 30 and there are 30 calculators in the shipment....
The merchant paid $300/30 = $10 per calculator
2 calculators were used for demonstrations, so 30 - 2 = 28 calculators were sold
Each of the 'sold' calculators brought in $10+$5 = $15
The total revenue was ($15)(28) = $420
The total profit was $420 - $300 = $120
This is an exact match for what we were told, so this MUST be the answer.
Final Answer: E
GMAT assassins aren't born, they're made,
Rich
The information in the prompt include a variety of nice 'round' numbers, so it's likely that the number of calculators in the shipment is also a round number AND divides evenly into 300. Only two of the answers 'fit' that idea - 25 and 30, so let's TEST THE ANSWERS and see if either of those values fits all of the information given in the prompt.
IF.... X = 30 and there are 30 calculators in the shipment....
The merchant paid $300/30 = $10 per calculator
2 calculators were used for demonstrations, so 30 - 2 = 28 calculators were sold
Each of the 'sold' calculators brought in $10+$5 = $15
The total revenue was ($15)(28) = $420
The total profit was $420 - $300 = $120
This is an exact match for what we were told, so this MUST be the answer.
Final Answer: E
GMAT assassins aren't born, they're made,
Rich
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The average price of the cost of the x calculators is 300/x dollars.BTGmoderatorAT wrote: ↑Sat Sep 16, 2017 4:53 amA merchant paid $300 for a shipment of x identical calculators. The merchant used 2 of the calculators as demonstrators and sold each of the others for $5 more than the average (arithmetic mean) cost of the x calculators. If the total revenue from the sale of the calculators was $120 more than the cost of the shipment, how many calculators were in the shipment?
A. 24
B. 25
C. 26
D. 28
E. 30
Is there a strategic approach to this question?
OA: E
(x - 2) calculators were sold for (300/x) + 5 dollars each, for a total revenue of:
(x - 2)[(300/x) + 5] = 300 + 5x - (600/x) - 10 = (300x - 600)/x + 5x - 10
Since the total revenue from the sale of the calculators was $120 more than the cost of the shipment:
(300x - 600)/x + 5x - 10 = 120 + 300
Multiplying by x, we have:
300x - 600 + 5x^2 - 10x = 120x + 300x
5x^2 - 130x - 600 = 0
x^2 - 26x - 120 = 0
(x - 30)(x + 4) = 0
x = 30 or x = -4
Since x can’t be negative, x = 30.
Answer: E
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The average cost of the x calculators is 300/x dollars.BTGmoderatorAT wrote: ↑Sat Sep 16, 2017 4:53 amA merchant paid $300 for a shipment of x identical calculators. The merchant used 2 of the calculators as demonstrators and sold each of the others for $5 more than the average (arithmetic mean) cost of the x calculators. If the total revenue from the sale of the calculators was $120 more than the cost of the shipment, how many calculators were in the shipment?
A. 24
B. 25
C. 26
D. 28
E. 30
Is there a strategic approach to this question?
OA: E
(x - 2) calculators were sold for (300/x) + 5 dollars each, for a total revenue of:
(x - 2)[(300/x) + 5] = 300 + 5x - (600/x) - 10 = (300x - 600)/x + 5x - 10
Since the total revenue from the sale of the calculators was $120 more than the cost of the shipment:
(300x - 600)/x + 5x - 10 = 120 + 300
Multiplying by x, we have:
300x - 600 + 5x^2 - 10x = 120x + 300x
5x^2 - 130x - 600 = 0
x^2 - 26x - 120 = 0
(x - 30)(x + 4) = 0
x = 30 or x = -4
Since x can’t be negative, x = 30.
Answer: E
Scott Woodbury-Stewart
Founder and CEO
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews