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### GMAT Club Daily Prep

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08 Aug 2019, 23:51
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Difficulty:

35% (medium)

Question Stats:

75% (03:14) correct 25% (03:26) wrong based on 73 sessions

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[GMAT math practice question]

Last month, the selling price of a certain product was $12. This month, the product’s price was cut by 20%. 165 more units of the product were sold this month than last month, and the total sales of the product this month were$420 higher than last month. How many units of the product were sold last month?

A. 400
B. 445
C. 485
D. 500
E. 520

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"Only $79 for 1 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Senior Manager Joined: 28 Jun 2019 Posts: 469 Re: Last month, the selling price of a certain product was$12. This mont  [#permalink]

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09 Aug 2019, 00:07
0.8×12%=9.6$(X+165)×9.6=420+12X 2.4X=1164 X=485 Option C Posted from my mobile device _________________ Always waiting Senior Manager Status: So far only Dreams i have!! Joined: 05 Jan 2015 Posts: 307 WE: Consulting (Computer Software) Last month, the selling price of a certain product was$12. This mont  [#permalink]

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09 Aug 2019, 00:34
Product SP last month: $12 Units sold last month : x Product SP this month : 80% of$12 = $9.6 As sales of the product this month were$420 higher than last month and number of units sold 165 more than last month:
Equation is as follows:

12x - 9.6(x+165) =420
2.4x = 1164 => x = 485
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Re: Last month, the selling price of a certain product was $12. This mont [#permalink] ### Show Tags 12 Aug 2019, 00:07 => Let $$n$$ be the number of units of the product sold last month. Then $$(n+165)(12)(\frac{1-20}{100}) – n*12 = 420.$$ Simplifying yields $$(n+165)(12)(0.8) – 12n = 165*12*(0.8) – 12n*(0.2) = 420.$$ So, $$12n*(0.2) = 165*12*(0.8) – 420$$ We solve this equation to find $$n = 485.$$ Therefore, the answer is C. Answer: C _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$79 for 1 month Online Course"
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