Percentage

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pullagurla: Senior | Next Rank: 100 Posts; Posts: 30; Joined: Tue Sep 29, 2009 7:04 pm; Thanked: 1 times

by pullagurla » Fri Aug 27, 2010 8:21 am

The price of lunch for 15 people was $207.00,
including a 15 percent gratuity for service. What was
the average price per person, EXCLUDING the
gratuity?
(A) $11.73
(B) $12.00
(C) $13.80
(D) $14.00
(E) $15.87

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Source: Beat The GMAT — Problem Solving | Fri Aug 27, 2010 8:21 am

RickH: Senior | Next Rank: 100 Posts; Posts: 46; Joined: Thu May 14, 2009 8:09 pm

by RickH » Fri Aug 27, 2010 8:34 am

The Answer is A, $11.73.

You need to do it like this:

1. Find 15% of $207, which is 31.05.
2. Subtract 31.05 from $207 to have the price without gratuity. This is $175.95
3. Divide $175.95 by 15 people.
4. Solutions: $11.73 average price per person.

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neerajkumar1_1: Master | Next Rank: 500 Posts; Posts: 270; Joined: Wed Apr 07, 2010 9:00 amFollowed by: 2 members; Thanked: 24 times

by neerajkumar1_1 » Fri Aug 27, 2010 8:35 am

pullagurla wrote:The price of lunch for 15 people was $207.00,
including a 15 percent gratuity for service. What was
the average price per person, EXCLUDING the
gratuity?
(A) $11.73
(B) $12.00
(C) $13.80
(D) $14.00
(E) $15.87

You are given the total amount for 15 people with gratuity as 207$.
And u are told to find price per person excluding gratuity..

So therefore First u find the total amount excluding gratuity...

So u can frame a equation..

1.15(oriignal)=207
therefore original = 207/1.15 = 180

hence price per person = 180/15 = 12

IMO: B

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wdgolden: Newbie | Next Rank: 10 Posts; Posts: 9; Joined: Tue Aug 17, 2010 10:55 am; Thanked: 2 times

by wdgolden » Fri Aug 27, 2010 8:47 am

Good point. There is a difference between 15% of 207, and a number plus 15% = 207.

207 - 15% = X; X = 175.95

X + 15% = 207; X = 180

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RickH: Senior | Next Rank: 100 Posts; Posts: 46; Joined: Thu May 14, 2009 8:09 pm

by RickH » Fri Aug 27, 2010 10:05 am

so what is the official answer?

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BastiG: Master | Next Rank: 500 Posts; Posts: 146; Joined: Sun Jun 13, 2010 5:05 am; Thanked: 7 times

by BastiG » Fri Aug 27, 2010 10:21 am

pullagurla wrote:The price of lunch for 15 people was $207.00,
including a 15 percent gratuity for service. What was
the average price per person, EXCLUDING the
gratuity?
(A) $11.73
(B) $12.00
(C) $13.80
(D) $14.00
(E) $15.87

I guess that the fastest way is so look at the answer choices and try to solve this backwards. I startet out with 13,8 and multiplied it with 15.
15*13,8=207
Now you can see that the answer has to be A or B. This took you about 12 seconds. (You can now take a guess between A/B --> 50/50 chance.) Or you can continue

The next step is to look at the gratuity fee. The graduity fee is 15/100 or 3/20. You quickly see by looking at the two possible answers that B is the only solution because 15*11,73 is something with XX,X5 at the end of the number and the price (Meal+ gratuity) is XX,00. You realise that there is no way that XX,X5*23/20=XX,00. So b is the answer.
With this hack you have a solution in about 30 seconds or even less.

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