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# If the price of a chocolate bar is doubled

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Intern
Joined: 03 Jul 2013
Posts: 27
Location: United States
Concentration: Finance, General Management
Schools: Mannheim '15
GPA: 3
WE: Human Resources (Consulting)
If the price of a chocolate bar is doubled  [#permalink]

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12 Sep 2013, 13:16
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35% (medium)

Question Stats:

68% (01:19) correct 32% (01:18) wrong based on 309 sessions

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If the price of a chocolate bar is doubled, by what percent will sales (quantity sold) of the chocolate bar decrease?

(1) For every 15 cent increase in price, the sales (quantity sold) will decrease by 10%

(2) Each chocolate bar now costs 99 cents

The QA seems wrong to me !! or am i wrong ?
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Joined: 02 Sep 2009
Posts: 55150
Re: If the price of a chocolate bar is doubled  [#permalink]

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12 Sep 2013, 13:29
2
If the price of a chocolate bar is doubled, by what percent will sales (quantity sold) of the chocolate bar decrease?

(1) For every 15 cent increase in price, the sales (quantity sold) will decrease by 10%. We don't know the price of the bar. Not sufficient.

(2) Each chocolate bar now costs 99 cents. We don't know how increase in price affects the quantity sold. Not sufficient.

(1)+(2) If we double the price it'll increase by 99 cents, so the sales must decrease by 99/15*10=66%. Sufficient.

Does this make sense?
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Intern
Joined: 03 Jul 2013
Posts: 27
Location: United States
Concentration: Finance, General Management
Schools: Mannheim '15
GPA: 3
WE: Human Resources (Consulting)
Re: If the price of a chocolate bar is doubled  [#permalink]

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12 Sep 2013, 13:50
1
Thank you Bunuel !! i guess i was sleeping while doing the question.

I kept on reading 15 PERCENT rather than 15 CENT in statement 1.
Director
Joined: 27 May 2012
Posts: 782
Re: If the price of a chocolate bar is doubled  [#permalink]

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25 Oct 2013, 04:21
Bunuel wrote:
If the price of a chocolate bar is doubled, by what percent will sales (quantity sold) of the chocolate bar decrease?

(1) For every 15 cent increase in price, the sales (quantity sold) will decrease by 10%. We don't know the price of the bar. Not sufficient.

(2) Each chocolate bar now costs 99 cents. We don't know how increase in price affects the quantity sold. Not sufficient.

(1)+(2) If we double the price it'll increase by 99 cents, so the sales must decrease by 99/15*10=66%. Sufficient.

Does this make sense?

sorry !
Although got the answer as C still can't understand how we get 66%.

after doubling the price becomes 99 cents so initially the price was 49.5 cents
now it says for every 15 cent increase the price decreased by 10 %

so a total increase of 49.5 cents took place, how many 15 cents increases are there?

so 49.5/15 = 3.3

meaning after 1st 15 cent increase price becomes 49.5 +15 = 64.5 and sales decreases by 10 %
after second 15 cent increase price becomes 79.5 and sales decreases by another 10 %
after third 15 cent increase price becomes 94.5 and sales decreases by another 10%
for the remaining 4.5 cents increase sales will decrease by less than 10 %

So I was expecting that sales would decrease by something between 30% - 35% .

What am I doing wrong ?
Thank you
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- Stne
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Re: If the price of a chocolate bar is doubled  [#permalink]

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25 Oct 2013, 04:26
1
stne wrote:
Bunuel wrote:
If the price of a chocolate bar is doubled, by what percent will sales (quantity sold) of the chocolate bar decrease?

(1) For every 15 cent increase in price, the sales (quantity sold) will decrease by 10%. We don't know the price of the bar. Not sufficient.

(2) We don't know how increase in price affects the quantity sold. Not sufficient.

(1)+(2) If we double the price it'll increase by 99 cents, so the sales must decrease by 99/15*10=66%. Sufficient.

Does this make sense?

sorry !
Although got the answer as C still can't understand how we get 66%.

after doubling the price becomes 99 cents so initially the price was 49.5 cents
now it says for every 15 cent increase the price decreased by 10 %

so a total increase of 49.5 cents took place, how many 15 cents increases are there?

so 49.5/15 = 3.3

meaning after 1st 15 cent increase price becomes 49.5 +15 = 64.5 and sales decreases by 10 %
after second 15 cent increase price becomes 79.5 and sales decreases by another 10 %
after third 15 cent increase price becomes 94.5 and sales decreases by another 10%
for the remaining 4.5 cents increase sales will decrease by less than 10 %

So I was expecting that sales would decrease by something between 30% - 35% .

What am I doing wrong ?
Thank you

Please read carefully: each chocolate bar now costs 99 cents. If we double the price it'll become 99*2=198 cents.
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Posts: 782
Re: If the price of a chocolate bar is doubled  [#permalink]

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25 Oct 2013, 04:36
Bunuel wrote:
stne wrote:
Bunuel wrote:
If the price of a chocolate bar is doubled, by what percent will sales (quantity sold) of the chocolate bar decrease?

(1) For every 15 cent increase in price, the sales (quantity sold) will decrease by 10%. We don't know the price of the bar. Not sufficient.

(2) We don't know how increase in price affects the quantity sold. Not sufficient.

(1)+(2) If we double the price it'll increase by 99 cents, so the sales must decrease by 99/15*10=66%. Sufficient.

Does this make sense?

sorry !
Although got the answer as C still can't understand how we get 66%.

after doubling the price becomes 99 cents so initially the price was 49.5 cents
now it says for every 15 cent increase the price decreased by 10 %

so a total increase of 49.5 cents took place, how many 15 cents increases are there?

so 49.5/15 = 3.3

meaning after 1st 15 cent increase price becomes 49.5 +15 = 64.5 and sales decreases by 10 %
after second 15 cent increase price becomes 79.5 and sales decreases by another 10 %
after third 15 cent increase price becomes 94.5 and sales decreases by another 10%
for the remaining 4.5 cents increase sales will decrease by less than 10 %

So I was expecting that sales would decrease by something between 30% - 35% .

What am I doing wrong ?
Thank you

Please read carefully: each chocolate bar now costs 99 cents. If we double the price it'll become 99*2=198 cents.

How do we know that the NOW stands for before doubling and not after doubling.

It would have been clearer if it was mentioned " before the price was doubled each bar cost 99 cents "
the second statement as of now could also imply that after the price is doubled the cost is now 99 cents.
_________________
- Stne
Math Expert
Joined: 02 Sep 2009
Posts: 55150
If the price of a chocolate bar is doubled  [#permalink]

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25 Oct 2013, 04:48
stne wrote:
Bunuel wrote:
stne wrote:
sorry !
Although got the answer as C still can't understand how we get 66%.

after doubling the price becomes 99 cents so initially the price was 49.5 cents
now it says for every 15 cent increase the price decreased by 10 %

so a total increase of 49.5 cents took place, how many 15 cents increases are there?

so 49.5/15 = 3.3

meaning after 1st 15 cent increase price becomes 49.5 +15 = 64.5 and sales decreases by 10 %
after second 15 cent increase price becomes 79.5 and sales decreases by another 10 %
after third 15 cent increase price becomes 94.5 and sales decreases by another 10%
for the remaining 4.5 cents increase sales will decrease by less than 10 %

So I was expecting that sales would decrease by something between 30% - 35% .

What am I doing wrong ?
Thank you

Please read carefully: each chocolate bar now costs 99 cents. If we double the price it'll become 99*2=198 cents.

How do we know that the NOW stands for before doubling and not after doubling.

It would have been clearer if it was mentioned " before the price was doubled each bar cost 99 cents "
the second statement as of now would also imply that after the price is doubled the cost is now 99 cents.

I see what you mean but notice that we are not told that the price IS doubled, we are told that "IF the price of a chocolate bar is doubled".
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Posts: 782
Re: If the price of a chocolate bar is doubled  [#permalink]

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25 Oct 2013, 05:07
Bunuel wrote:
I see what you mean but notice that we are not the price IS doubled, we are told that "IF the price of a chocolate bar is doubled".

Correct ! after in dept introspection , NOW does seem to apply before the price was increased, Thank you for clearing that.

How ever I am not able to understand the concept behind $$\frac{99}{15*10}$$

how are we calculating the percent decrease for the remaining 9 cents.?

for the 90 cents 60 % decrease is OK , but I am struggling to understand how we are dividing by 10?

Could use a little help here.

Thank you
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- Stne
Math Expert
Joined: 02 Sep 2009
Posts: 55150
Re: If the price of a chocolate bar is doubled  [#permalink]

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25 Oct 2013, 07:23
1
stne wrote:
Bunuel wrote:
I see what you mean but notice that we are not the price IS doubled, we are told that "IF the price of a chocolate bar is doubled".

Correct ! after in dept introspection , NOW does seem to apply before the price was increased, Thank you for clearing that.

How ever I am not able to understand the concept behind $$\frac{99}{15*10}$$

how are we calculating the percent decrease for the remaining 9 cents.?

for the 90 cents 60 % decrease is OK , but I am struggling to understand how we are dividing by 10?

Could use a little help here.

Thank you

Please read carefully. We are not dividing by 10. It's 99/15*10 not 99/(15*10).

For every 15 cent increase in price, the sales (quantity sold) will decrease by 10%:
If the price increase by 15 cents the sales decrease by 15/15*10=10%.
If the price increase by 30 cents the sales decrease by 30/15*10=20%.
If the price increase by 45 cents the sales decrease by 45/15*10=30%.
...
If the price increase by 99 cents the sales decrease by 99/15*10=66%.

Hope it's clear.
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Director
Joined: 27 May 2012
Posts: 782
Re: If the price of a chocolate bar is doubled  [#permalink]

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25 Oct 2013, 08:25
Bunuel wrote:
stne wrote:
Bunuel wrote:
I see what you mean but notice that we are not the price IS doubled, we are told that "IF the price of a chocolate bar is doubled".

Correct ! after in dept introspection , NOW does seem to apply before the price was increased, Thank you for clearing that.

How ever I am not able to understand the concept behind $$\frac{99}{15*10}$$

how are we calculating the percent decrease for the remaining 9 cents.?

for the 90 cents 60 % decrease is OK , but I am struggling to understand how we are dividing by 10?

Could use a little help here.

Thank you

Please read carefully. We are not dividing by 10. It's 99/15*10 not 99/(15*10).

For every 15 cent increase in price, the sales (quantity sold) will decrease by 10%:
If the price increase by 15 cents the sales decrease by 15/15*10=10%.
If the price increase by 30 cents the sales decrease by 30/15*10=20%.
If the price increase by 45 cents the sales decrease by 45/15*10=30%.
...
If the price increase by 99 cents the sales decrease by 99/15*10=66%.

Hope it's clear.

Right ! Thank you +1
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GMAT 1: 750 Q48 V44
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Re: If the price of a chocolate bar is doubled  [#permalink]

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22 Nov 2016, 18:32
I chose E because I was not sure the 15¢ increase relating to a 10% decrease in sales was a linear relationship. If we double the price of the chocolate bar we are inducing a price increase of 99¢ which is not divisible by 15¢.

Is it wise to assume cost/change relationships could be presented with the same type of wording in the actual test? I have not come across one worded this way exactly in my practice tests.
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Re: If the price of a chocolate bar is doubled  [#permalink]

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05 Jan 2018, 04:48
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Re: If the price of a chocolate bar is doubled   [#permalink] 05 Jan 2018, 04:48
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