If the price of a chocolate bar is doubled

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.

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".

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

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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