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A business school reduced its class size by 16%, but then increased it

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A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 05:54
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Re: A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 06:13
Bunuel wrote:
A business school reduced its class size by 16%, but then increased it by 25% of the new amount. What was the net percent change in the size of the business school class?

(A) a 5% decrease
(B) a 9% decrease
(C) a 5% increase
(D) a 9% increase
(E) no net change


Initial 100, reduced to 84.
New number is 84 * (5/4)= 105, so 5% net increase.
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Re: A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 06:29
Bunuel wrote:
A business school reduced its class size by 16%, but then increased it by 25% of the new amount. What was the net percent change in the size of the business school class?

(A) a 5% decrease
(B) a 9% decrease
(C) a 5% increase
(D) a 9% increase
(E) no net change


For such questions, we can just use multipliers to speed up the calculation.

Assume the class size to be 100. The new size would be = 100 * 0.84 * 1.25 = 105. Hence, 5% increase. C is the answer.
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Re: A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 06:36
Bunuel wrote:
A business school reduced its class size by 16%, but then increased it by 25% of the new amount. What was the net percent change in the size of the business school class?

(A) a 5% decrease
(B) a 9% decrease
(C) a 5% increase
(D) a 9% increase
(E) no net change



16.........then 25

there will be a positive change.

So, option, A, B and E are eliminated.

25- 16 = 9.....thus i cancelled this option too

C is the correct answer.
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Re: A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 06:55
KSBGC wrote:
Bunuel wrote:
A business school reduced its class size by 16%, but then increased it by 25% of the new amount. What was the net percent change in the size of the business school class?

(A) a 5% decrease
(B) a 9% decrease
(C) a 5% increase
(D) a 9% increase
(E) no net change



16.........then 25

there will be a positive change.

So, option, A, B and E are eliminated.

25- 16 = 9.....thus i cancelled this option too

C is the correct answer.


KSBGC: This approach - of judging whether it is going to be positive or negative without actually calculating - wouldn't always work :)

Think about the following scenario - the class size first decreases by 16% and then increases by 18%. Would you still say that there would be a net positive change?

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Re: A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 07:06
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anud33p wrote:
KSBGC wrote:
Bunuel wrote:
A business school reduced its class size by 16%, but then increased it by 25% of the new amount. What was the net percent change in the size of the business school class?

(A) a 5% decrease
(B) a 9% decrease
(C) a 5% increase
(D) a 9% increase
(E) no net change



16.........then 25

there will be a positive change.

So, option, A, B and E are eliminated.

25- 16 = 9.....thus i cancelled this option too

C is the correct answer.


KSBGC: This approach - of judging whether it is going to be positive or negative without actually calculating - wouldn't always work :)

Think about the following scenario - the class size first decreases by 16% and then increases by 18%. Would you still say that there would be a net positive change?

Cheers
AA



you are correct . In % base is superb important. i used guessing technique in above cases but it won't work in all cases. the thing u need is experience. Someone dealing with % cases for long time can guess that there will be a positive change.


the class size first decreases by 16% and then increases by 18%.

here change is so close that there could be a negative change. guess .

Thnks.
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A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 07:23
Quote:
you are correct . In % base is superb important. i used guessing technique in above cases but it won't work in all cases. the thing u need is experience. Someone dealing with % cases for long time can guess that there will be a positive change.


the class size first decreases by 16% and then increases by 18%.

here change is so close that there could be a negative change. guess .

Thnks.


Haha, fair enough. I wouldn't doubt the discretion of a man who is into Finance & Accounting. You surely would have a better number sense than most :)

Cheers
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Re: A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 08:09
Bunuel wrote:
A business school reduced its class size by 16%, but then increased it by 25% of the new amount. What was the net percent change in the size of the business school class?

(A) a 5% decrease
(B) a 9% decrease
(C) a 5% increase
(D) a 9% increase
(E) no net change



Given: A business school reduced its class size by 16%, but then increased it by 25% of the new amount.

Asked; What was the net percent change in the size of the business school class?

Let the size of class be x

A business school reduced its class size by 16%,
Class size becomes (100%-16%) = .84x

then increased it by 25% of the new amount.
Class size becomes = (100%+25%).84x = 1.25 * .84 x = 1.05x

1.05x = (100%+5%)x

There is overall increase of 5% in class size

IMO C
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Re: A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 08:24
The class size decreased by 16%, meaning it has now become 0.84.
It is increased after the reduction by 25% means that the new class size is now 1.25*0.84
1.25*0.84= 0.125*8.4 = 8.4/8=1.05.
Hence the class has increased by 5%.

Answer is C.

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Re: A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 09:31
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Let the size of class be x
X*0.84*1.25 = 1.05x

((1.05x - x)/x)* 100

Ans -> 5% increase

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Re: A business school reduced its class size by 16%, but then increased it  [#permalink]

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New post 11 Aug 2019, 09:52
Bunuel wrote:
A business school reduced its class size by 16%, but then increased it by 25% of the new amount. What was the net percent change in the size of the business school class?

(A) a 5% decrease
(B) a 9% decrease
(C) a 5% increase
(D) a 9% increase
(E) no net change


let class = 100
so net effective change ; 100*.84*1.25 ; 105 ; i.e 5% increase from 100
IMO C
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Re: A business school reduced its class size by 16%, but then increased it   [#permalink] 11 Aug 2019, 09:52
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