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clock tick tick - it gmat time

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by canuckclint » Tue Nov 04, 2008 10:43 pm
A clock store sold a certain clock to a collector for 20 percent more than the store had originally paid for the clock. When the collector tried to resell the clock to the store, the store bought it back at 50 percent of what the collector had paid. The shop then sold the clock again at a profit of 80 percent on its buy-back price. If the difference between the clock's original cost to the shop and the clock's buy-back price was $100, for how much did the shop sell the clock the second time?

$270
$250
$240
$220
$200
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Source: — Problem Solving |

Re: clock tick tick - it gmat time

by parallel_chase » Tue Nov 04, 2008 11:57 pm
canuckclint wrote:A clock store sold a certain clock to a collector for 20 percent more than the store had originally paid for the clock. When the collector tried to resell the clock to the store, the store bought it back at 50 percent of what the collector had paid. The shop then sold the clock again at a profit of 80 percent on its buy-back price. If the difference between the clock's original cost to the shop and the clock's buy-back price was $100, for how much did the shop sell the clock the second time?

$270
$250
$240
$220
$200
Let x be the initial cost

120%x = first selling price

120%x * 50% = buy back price

120%x * 50% * 80% + 120%x * 50% = second selling price

x - 120%x * 50% = 100
x - 6x/10 = 100
4x = 1000
x = 250

Insert the value of x in second selling price

120%x * 50% * 80% + 120%x * 50%

=> 48x/100 + 6x/10

=> 48*250/100 + 6*250/10

=> 24*5 + 6*25 = 120 + 150 = 270

OA?
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by vishubn » Wed Nov 05, 2008 12:16 am
Difference given

x-.5(1.2)x=100
x-.6x=100
.4x=100
x=1000/4
x=250$ is the original price

So he sold for 300$
and buy back was 150$
and sold it 80 percent profit which is 150+.8(150)=
150+120
answer is 270$
Oa??

Vishu
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Re: clock tick tick - it gmat time

by dileepsinha » Wed Nov 05, 2008 12:29 am
canuckclint wrote:A clock store sold a certain clock to a collector for 20 percent more than the store had originally paid for the clock. When the collector tried to resell the clock to the store, the store bought it back at 50 percent of what the collector had paid. The shop then sold the clock again at a profit of 80 percent on its buy-back price. If the difference between the clock's original cost to the shop and the clock's buy-back price was $100, for how much did the shop sell the clock the second time?

$270
$250
$240
$220
$200
let 100 be the shop's cost price
collector's cost price=120
shop'e buy back price=60
shop's reselling price=108
if (100-60)>>$100
=>40 ->100 (2.5 times)
=> 108=(108+108+54)=270 (2.5 times of 108)
I did it orally.
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by raunekk » Wed Nov 05, 2008 3:30 am
let x be the shop's cost price
collector's cost price=1.20 x
shop'e buy back price=.60 x
shop's reselling price=1.08 x


difference between the clock's original cost to the shop and the clock's buy-back price = 100 = x - 0.60 x
i.e 0.40x = 100

x = 250

now,shop's reselling price=1.08 x = 1.08 * 250 = 270

thus,270

(A)
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by alltimeacheiver » Thu May 05, 2011 1:26 am
can anyone tell me that how we got 1.08%. Acc to me if it is 60 percent sale happned second time then we are maing 80 percent profit of 60 percent purchanse price. seems to be like 0.6*0.8=0.48. pls tell me th4 logic guys that how u r getting 1.08
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by GMATGuruNY » Thu May 05, 2011 3:42 am
canuckclint wrote:A clock store sold a certain clock to a collector for 20 percent more than the store had originally paid for the clock. When the collector tried to resell the clock to the store, the store bought it back at 50 percent of what the collector had paid. The shop then sold the clock again at a profit of 80 percent on its buy-back price. If the difference between the clock's original cost to the shop and the clock's buy-back price was $100, for how much did the shop sell the clock the second time?

$270
$250
$240
$220
$200
I would guess and check.

Let cost = 100.
Selling price = (1.2)*100 = 120.
Buy-back price = (.5)*120 = 60.
Cost - buy-back price = 100-60 = 40.

Too small. Needed difference = 100.
Since 100/40 = 2.5, all the values above must be multiplied by 2.5.

Thus:
Cost = (2.5)*100 = 250.
Buy-back price = (2.5)*60 = 150.

Thus, second selling price = (1.8)*150 = 270.

The correct answer is A.
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by crisro » Sat Sep 01, 2012 9:52 am
alltimeacheiver wrote:can anyone tell me that how we got 1.08%. Acc to me if it is 60 percent sale happned second time then we are maing 80 percent profit of 60 percent purchanse price. seems to be like 0.6*0.8=0.48. pls tell me th4 logic guys that how u r getting 1.08
It happened To me too! I didn't pay enough attention reading the problem, but it says: sold the clock again at a profit of 80 percent on its buy-back price.
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