The charge for a single room at Hotel P is 25 percent less than the ch

Question

The charge for a single room at Hotel P is 25 percent less than the charge for a single room at Hotel R and 10 percent less than the charge for a single room at Hotel G. The charge for a single room at Hotel R is what percent greater than the charge for a single room at Hotel G ?

A. 15%
B. 20%
C. 40%
D. 50%
E.150%

A. 15%
B. 20%
C. 40%
D. 50%
E. 150%

I solved the the problem as follows:
Let rate in R = 100x
then P = 75x

G = 100y
P = 90y

Thus 
75x=90y
or x = 1.20 y
Ans R = 120y
so increase = 20%

But I tried first to solve the problem as follows:
p = 100
R = 120
G = 110
and Failed Please help on my second effort.

Bunuel · Accepted Answer

As everything is linked with P then:

0.75R=P=0.9G ;

75R=90G ;

\frac{R}{G}=\frac{90}{75}=1.2 .

Answer: B.

As for your second approach. The numbers are incorrect:
If R=120 then P=90 (not 100);
If G=110 then P=99 (not 100);
If P=100 then R=100/0.75=~133.3 and G=100/0.9=~111.1.

DJ1986 · Answer

I saw this question at the very end of a GMAC practice test and I had like 30 seconds to do it so this was the fastest way I could come up with:

P=(3/4)R
p=(9/10)G

(9/10)G=(3/4)R
12/10G=R
12/10=20% greater Answer B

sumit1854 · Answer

This is a example of Combined Ratios since we need to compare one thing which is common to two other things separately.
Lets consider that charge for Hotel R is $100 then the charge for Hotel P becomes $ 75 (100-75). Similarly considering the charge for Hotel G as $100 the charge for Hotel becomes $ 90 (100-10).
Reducing it to ratios P:R:=75:100 i.e. P:R:=3:4
Similarly P:G:=90:100 i.e. P:G:=9:10
We cannot instantly combine these ratios into a single ratio since the terms for P are different.
So we need to convert these two ratios to combined ration by multiplying first ration with 3 which then becomes 9:12.
Hence the combined ration becomes P:R:G:=9:12:10 which implies that the ratio for R:G is 12:10
So if the charge at Hotel G is $100 then charge at Hotel R becomes $120 or in other words 20% higher.

PareshGmat · Answer

Answer = B 20%

Please refer below:

EMPOWERgmatRichC · Answer

Hi All,

This question can be solved by TESTing VALUES.

Let's TEST...
The single room charge at Hotel R = $100
The single room charge at Hotel P = $75
The single room charge at Hotel G = about $83

This question uses the phrase "what percent greater…" which means that we have to use the Percentage Change Formula:

Percentage Change = (New - Old)/Old.

In this scenario, the price at Hotel R is the "New" number and the price at Hotel G is the "Old" number.

Using the numbers we're TESTing, we have…

(100 - 83)/83 = 17/83

Since we estimated that "83", the correct answer will be approximately...

17/85 = 1/5 = 20%

Final Answer:  B

GMAT assassins aren't born, they're made, 
Rich

umadurga · Answer

I've considered P=100(as everything is based on P)
Thus R = 125 and G = 110
% change = (125-110)/125=12
Not sure where am I going wrong. Kindly explain.

EMPOWERgmatRichC · Answer

Hi umadurga,

You have to be very careful here - especially when dealing with percent change.

To start, the number 100 is NOT "25% less" than 125... it's only 20% less. Since 125 is the 'base' number, you would have to subtract (25% of 125) from 125... and that would not be a 'nice' number (it would be 125 - 31.25 = 93.75).

If you read my post (a few posts up the page from your post), you'll see how you can make R=100 and proceed from there with relatively nice values.

GMAT assassins aren't born, they're made,
Rich

JeffTargetTestPrep · Answer

We can let the charge for a room at hotel P = p, the charge for a room at hotel G = g, and the charge for a room at hotel R = r.

We are given that the charge for a single room at Hotel P is 25 percent less than the charge for a single room at Hotel R and 10 percent less than the charge for a single room at Hotel G. Thus:

p = 0.75r

p = 3r/4

AND

p = 0.9g

p = 9g/10

We need to determine what percent greater the charge is for hotel R than for hotel G. Thus, we need to evaluate (r - g)/g x 100. However, we first need to get variables r and g in terms of p.

r = 4p/3

AND

g = 10p/9

Substitute 4p/3 for r and 10p/9 for g and we have:

(r - g)/g x 100

x 100

2/10 x 100 = 20 percent

Alternate solution:

We can let the charge for a room at hotel P = p, the charge for a room at hotel G = g, and the charge for a room at hotel R = r.

We are given that the charge for a single room at Hotel P is 25 percent less than the charge for a single room at Hotel R and 10 percent less than the charge for a single room at Hotel G. Thus:

p = .75r

And

p = .9g

Since both right-hand expressions are equal to p, we set them equal to each other, and then we solve for r.

.75r = .9g

r = 1.2g

Thus, Hotel R’s rate is 20% greater than Hotel G’s rate.

Answer: B

Karastoyanov · Answer

The charge for a single room at Hotel P is 25 percent less than the charge for a single room at Hotel R and 10 percent less than the charge for a single room at Hotel G. The charge for a single room at Hotel R is what percent greater than the charge for a single room at Hotel G ?

A. 15%
B. 20%
C. 40%
D. 50%
E.150%

A. 15%
B. 20%
C. 40%
D. 50%
E.150%

Please tell me where am I wrong?

We have 3 hotels - P, R and G. Let the R hotel price is 100$, so hotel P is 25% less => which is 75$. Hotel G is 10% more expensive than hotel P => 75+10%=82,5$.
So what we have:
Hotel R = 100$
Hotel G = 82,5$

(100$-82,5$)/82,5$= 21%

I do understand logic behind the proper solution, but can anybody give the solution using not proportions, but real money? TJNAKS

Bunuel · Answer

If R = 100, then:
P = 75 (The charge for a single room at Hotel P is 25 percent less than the charge for a single room at Hotel R)
G = 250/3 ≈ 83.3333. (The charge for a single room at Hotel P is 10 percent less than the charge for a single room at Hotel G.)

Karastoyanov · Answer

Thank you for the quick answer, but where these 250 are from? Thanks

Bunuel · Answer

The charge for a single room at Hotel P is 10 percent less than the charge for a single room at Hotel G:

75 = 9/10*G;
750/9 = G;
250/3 = G.

MITIMITIM · Answer

Hi EMPOWERgmatRichC why is for example 120-100/100 and not 120-100/120 I mean in the formula (new - original)/original, how can I decide which one is the original? Many thanks

EMPOWERgmatRichC · Answer

Hi gastoneMIT,

When a question asks "what percent greater..." or "what percent less...." the "original" number is the one that you are COMPARING TO. For example...

"X is what percent greater than Y" --> (New - Original)/(Original) = (X - Y)/Y

Using numbers instead of variables...

"120 is what percent greater than 100" --> (New - Original)/(Original) = (120 - 100)/100
 
GMAT assassins aren't born, they're made,
Rich

woohoo921 · Answer

EMPOWERgmatRichC

Thank you for your helpful explanation. I followed your approach but was frustrated when I did not get an answer that exactly matched one of the answer choices. I believed that I needed my answer to exactly match the answer choice because I did not see a word such as "approximate" in the question stem. How did you know that it was okay to estimate? Thank you for your time.

EMPOWERgmatRichC · Answer

Hi woohoo921, If you look at the 5 answer choices, you can see that they are fairly 'spread out' percentages - which often means that you can potentially use estimation at some point in your calculations. If the answers had been really 'close' to one another (for example, 19%, 20%, 21%, 22%, 23%), then far more specific calculations would obviously be required (as any type of minor rounding error could lead you to an answer that is too high or too low). GMAT assassins aren't born, they're made, Rich Contact Rich at: Rich.C@empowergmat.com

Tanchat · Answer

Bunuel

Does "The charge for a single room at Hotel P is 25 percent less than the charge for a single room at Hotel R" not mean : Charge for R - Charge for P = 0.25 Charge for P ?

Bunuel · Answer

Say the charge for a single room at R is $100.

Then the charge for a single room at Hotel P is 25 percent less than the charge for a single room at Hotel R, would mean that the charge for a single room at P is $75 (25% less than at R).

If you want to express it algebraically, then P = R - 0.25R = 0.75R.

Does this make sense?

GMATGuruNY · Answer

The charge for a single room at Hotel P is 25 percent less than the charge for a single room at Hotel R. 
If R=100, then P=75, implying that  \frac{R}{P} = \frac{100}{75} = \frac{4}{3}

The charge for a single room at Hotel P is 10 percent less than the charge for a single room at Hotel G. 
If G=100, then P=90, implying that  \frac{P}{G} = \frac{90}{100} = \frac{9}{10}

The charge for a single room at Hotel R is what percent greater than the charge for a single room at Hotel G? 
 \frac{R}{G} = \frac{R}{P} * \frac{P}{G} = \frac{4}{3} * \frac{9}{10} = \frac{12}{10}

In the resulting ratio, the value of R (12) is 20% greater than the value of G (10).

B

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The charge for a single room at Hotel P is 25 percent less than the ch

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