MGMAT MISTAKE IN TEST PROBLEM ???

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MGMAT MISTAKE IN TEST PROBLEM ???

by PAB2706 » Sun Mar 15, 2009 12:01 am
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

guess there is a problem with this MGMAT test problem. it is saying profit of 80% over buy back price. but while soling they are taking 8% to get the answer A
Source: — Problem Solving |

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by DanaJ » Sun Mar 15, 2009 12:13 am
Say initial purchase price by the store = x.
They sell the clock at a 20% profit, making the selling price 120% of x or 1.2x.
Then the collector sells the clock back at 50% of the buying price, or 50% of 1.2x. This means 0.5*1.2x = 0.6x.
The shop re-sells the clock at a profit of 80% of its buyback price, or 180% of 0.6x, which is 1.8*0.6x = 1.08x - and this is what we need to find out.

Now, we are told that the difference between the clock's original cost to the shop and the clock's buy-back price was $100, meaning that x - 0.6x = 100 or that 0.4x = 100.
This makes x = 250 and we are now able to find the answer we're looking for: 1.08*250 = 270.

I got the OA....

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Re: MGMAT MISTAKE IN TEST PROBLEM ???

by Vemuri » Sun Mar 15, 2009 12:16 am
Answer is A ($270).

Lets assume that the original price the store paid for the clock was $x.

They sold it for 20% profit to a collector ==> $1.2x
The store bought it back at 50% of what the collector had paid ==> $0.6x
The store now sold it at 80% profit on buy back price ==> $0.6x(1+4/5)
==> $0.6x(9/5)
==> $5.4x/5

Given that the difference between the clock's original cost to the shop and the clock's buy-back price was $100
==> $x-$0.6x=100
==> $0.4x=100
==> x=$250 <-- This is the original price the store paid

The question is asking, for how much did the shop sell the clock the second time?
==> $5.4x/5 (insert the value of x & we have our answer)
==> $5.4*250/5
==> $5.4*50
==> $270

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Diagramatic presentation

by gmat740 » Sun Mar 15, 2009 12:42 am
I am doing the same thing as done by GMAT Destroyer

But My approach is diagramatic one


Store ==> collector

x ==> 1.2x

0.6x <== 1.2 x

Now the stores sells again @ 80% profit of 0.6x i.e 1.08x(to be calculated)

its given that
x-0.6x = $100

So,
x = $250

When we know X
so we can easily calculate 1.08x=$270

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by PAB2706 » Sun Mar 15, 2009 5:09 am
OH FREAK........ I am sorry....such a daft... hope i dnt make such mistakes in the main GMAT.

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by gmat740 » Sun Mar 15, 2009 5:44 am
I am sorry....such a daft
what do you mean by DRAFT??