Increasing the original price of an article by 15 percent : Problem Solving (PS)

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Re: Increasing the original price of an article by 15% and then [#permalink]

09 Mar 2013, 22:24

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chiccufrazer1 wrote:

Increasing the original price of an article by 15% and then increasing the new price by 15% again is equivalent to increasing the original price by what %?

A.34 B.40 C.68 D.88 E.102

Hey guys this might be as simple as abc for a math problem to you but not me..anyway this is how i did it after reading a gmat study guide on percents from platinumgmat albeit i dd not pretty well understand it..the two percentages in decimal form,will be as 0.15 each..x(0.15)multiply(0.15) the result is 1.3325x..to one decimal place it is 1.3x..i then found the percentage increase {(end value - start value)/start value)}*100 hence {(1.3225x-x)/x)}*100 =32.25 (to the nearest whole number;32..but among the answer choices there is no 32)how did i get it wrong?please help

To INCREASE a certain number by 15%, you will have to multiply by 1.15
To DECREASE a certain number by 15%, you will have to multiply by 0.85.
To find what 15% of a certain number is, you will have to multiply by 0.15

Lets say the original price of the article is 10$
Multiplying 10 by 1.15 we get 11.5$
Now multiplying 11.5 by 1.15 again we get 13.225 which is the same as increasing 10 by 32%.
So the answer you got is correct.

If the answer choices aren't incorrect, you would be best served to choose the closest possible answer choice i.e. A and move on.

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Re: Increasing the original price of an article by 15% and then [#permalink]

10 Mar 2013, 05:49

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chiccufrazer1 wrote:

Increasing the original price of an article by 15% and then increasing the new price by 15% again is equivalent to increasing the original price by what %?

A. 34
B. 40
C. 68
D. 88
E. 102

Show Spoiler

Hey guys this might be as simple as abc for a math problem to you but not me..anyway this is how i did it after reading a gmat study guide on percents from platinumgmat albeit i dd not pretty well understand it..the two percentages in decimal form,will be as 0.15 each..x(0.15)multiply(0.15) the result is 1.3325x..to one decimal place it is 1.3x..i then found the percentage increase {(end value - start value)/start value)}*100 hence {(1.3225x-x)/x)}*100 =32.25 (to the nearest whole number;32..but among the answer choices there is no 32)how did i get it wrong?please help

The actual increase would be a little more that 15 + 15 = 30%, only A fits.

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You can find other question here;
PS: search.php?search_id=tag&tag_id=191
DS; search.php?search_id=tag&tag_id=192

Hope it helps.

sandeepdey

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Re: Increasing the original price of an article by 15% and then [#permalink]

10 Mar 2013, 08:52

chiccufrazer1 wrote:

Increasing the original price of an article by 15% and then increasing the new price by 15% again is equivalent to increasing the original price by what %?

A. 34
B. 40
C. 68
D. 88
E. 102

Show Spoiler

Hey guys this might be as simple as abc for a math problem to you but not me..anyway this is how i did it after reading a gmat study guide on percents from platinumgmat albeit i dd not pretty well understand it..the two percentages in decimal form,will be as 0.15 each..x(0.15)multiply(0.15) the result is 1.3325x..to one decimal place it is 1.3x..i then found the percentage increase {(end value - start value)/start value)}*100 hence {(1.3225x-x)/x)}*100 =32.25 (to the nearest whole number;32..but among the answer choices there is no 32)how did i get it wrong?please help

During successive increment or decrements we can apply below mentioned logic. Helps to calculate faster

Let the price of a commodity is increased by a% and then b% then the final increment will be

1 + a/100 + b/100 + ab/10000

Now the same logic can be applied with decrements also with just changing the signs.
Let for example price of commodity is increased by a% and then decreased by b% then the resulting increase/decrease will be

1 + a/100 - b/100 -ab/10000

For the above question the approach will be

1 + 0.15 + 0.15 + 0.0225 = 1.3225 ==> 32.25%
Closest answer is A

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Re: Increasing the original price of an article by 15 percent [#permalink]

11 Jul 2014, 01:10

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Initial Price = 100

15% increase = 115

Again 15% increase on new price $= 115 + 115 * \frac{15}{100}$

= 115 + 117.25

= 132.25

Percentage Increase = 132.25 - 100 = 32.25%

holeintheboat

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Re: Increasing the original price of an article by 15 percent [#permalink]

11 Jul 2014, 05:50

Original Price be P

Increasing by 15% => New price = 1.15 P
Again Increasing it by 15 % => Final Price = 1.15*1.15 P = 1.3225 { 115^2 = 11*12 25 = 13225}

Hence increase is (1.3225 - 1)*100% = 32.25%

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Re: Increasing the original price of an article by 15 percent [#permalink]

30 Mar 2016, 14:32

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consider base price as $100
15% increase = 1.15*100 = 115
Another 15% increase on new price = 1.15 * 115 = 132.25
therefore a 32.25% increase

Correct ans - A

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Re: Increasing the original price of an article by 15 percent [#permalink]

11 Feb 2017, 17:06

Lets say P=100 $ --> 100*15%=115$ = P1

115+15%*(115)= P2

You can think 115 as 100 + 10 + 5 and take 15% of each one:
15%* 100 = 15
15%*10= 1,5
15%*(2*5)=1,5-->15%*5=0,75

The answer is 115+15+1,5+0,75= 132,25 --> Answer A

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Re: Increasing the original price of an article by 15 percent [#permalink]

12 Feb 2017, 02:32

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fiendex wrote:

Increasing the original price of an article by 15 percent and then increasing the new price by 15 percent is equivalent to increasing the original price by

A) 32.25%
B) 31.00%
C) 30.25%
D) 30.00%
E) 22.50%

Shortest method will be -

$15 + 15 + \frac{(15*15)}{100}$

= 30 + 2.25

= 32.25%

Hence, correct answer will be (A) 32.25%

B

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Re: Increasing the original price of an article by 15% and then [#permalink]

20 May 2017, 05:29

Since the nearest ans to 32 % is option A. I chose option A.

Let 100 be original price.
15 % increase = 115
15% increase = little more then 15 = 132

Hence 32 % increase.

Alternatively Solution:

15 + 15 + $\frac{(15)(15)}{100}$

30 +$\frac{225}{100}$

30 + 2.25

32.25

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Re: Increasing the original price of an article by 15 percent [#permalink]

17 Oct 2020, 06:09

OFFICIAL GMAT EXPLANATION

If p is the original price, then the 15 percent increase in price results in a price of 1.15p. The next 15 percent increase in price results in a price of 1.15(1.15p), or 1.3225p. Thus, the price increased by 1.3225p – p = 0.3225p, or 32.25% of p. The best answer is A.

B

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Re: Increasing the original price of an article by 15 percent [#permalink]

17 Oct 2020, 08:56

fiendex wrote:

Increasing the original price of an article by 15 percent and then increasing the new price by 15 percent is equivalent to increasing the original price by

A) 32.25%
B) 31.00%
C) 30.25%
D) 30.00%
E) 22.50%

Let's assume the initial price is $100 and we increase it by 15%, which will be $15 and the total would be $115. Then we increase it again by 15% ---> $115*15% = $17.25
$115+$17.25 = $132.25

Hence the answer is 32.25%

Choice is A.

Kindly give kudos if correct.

B

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Re: Increasing the original price of an article by 15 percent [#permalink]

27 Jan 2023, 02:38

KarishmaB This may be a very rudimentary question, and if so, I apologize in advance... But I originally got this wrong because I did 0.15*0.15 and got 0.0225, which clearly doesn't make sense. Can you please explain why this approach is incorrect? Is it because we have to take 15% of the resulting figure, not 15% of the 15% (which results in too small of a fraction)?

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KarishmaB

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Re: Increasing the original price of an article by 15 percent [#permalink]

31 Jan 2023, 02:19

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ayakik wrote:

KarishmaB This may be a very rudimentary question, and if so, I apologize in advance... But I originally got this wrong because I did 0.15*0.15 and got 0.0225, which clearly doesn't make sense. Can you please explain why this approach is incorrect? Is it because we have to take 15% of the resulting figure, not 15% of the 15% (which results in too small of a fraction)?

15% of a number is a small part of it.
For example, 15% of 100 is just 15.

But when we "increase a number by 15%" we are making it larger.
We say this is 100 + 15/100 of 100 = 115

So when we want to "increase" a number by 15%, we multiply it by (1 + 15/100) i.e. by 115/100. The number increases.
When we want to further increase it by 15%, we multiply it by another 115/100.

So we get N * 115/100 * 115/100 as the new number which is greater than the original. number N.

When we take N * 15/100 * 15/100, we are effectively finding the 15% of the 15% of the number. So if the number is 100, 15% of its 15% becomes
15/100 * 15/100 * 100 = 2.25

B

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Re: Increasing the original price of an article by 15 percent [#permalink]

31 Jan 2023, 23:30

KarishmaB This makes a lot of sense now. Thank you so much for the comprehensive explanation!

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Re: Increasing the original price of an article by 15 percent [#permalink]

27 Jul 2023, 06:13

The 15% increase of x in the first round increases x by a certain amount. The 15% increase in the second round is applied to a higher number, so will yield a larger change.

gmatclubot

Re: Increasing the original price of an article by 15 percent [#permalink]

27 Jul 2023, 06:13

GMAT Problem Solving (PS) Questions

Increasing the original price of an article by 15 percent