33- 70 Arithmetics

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phoenix9801: Master | Next Rank: 500 Posts; Posts: 190; Joined: Thu Jan 14, 2010 8:29 pm; Thanked: 2 times

by phoenix9801 » Sat Jul 10, 2010 11:03 pm

Hi, can someone please help to explain by step-by-step instructions (in detail) in the most simplest way and clear to understand. Would Greatly appreciate it.

1-

What was the price at which a merchant sold a certain appliance?

(1) the merchant's gross profit on the appliance was 20 percent of the price at which the merchant sold the appliance.

(2) The price at which the merchant sold the appliance was $50 more than the merchant's cost of the appliance.

2-

Mary persuaded n friends to donate $500 each to her election champaign, and then each of these n friends persuaded n more people to donate $500 each to Mary's campaign. if no one donated more than once and if there were no other donations, what was the value of n?

(1) The first n people donated 1/16 od total amount donated.

(2) the total amount donated was $120,000

Last edited by phoenix9801 on Mon Jul 12, 2010 4:00 pm, edited 2 times in total.

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gmatmachoman: Legendary Member; Posts: 2326; Joined: Mon Jul 28, 2008 3:54 amFollowed by: 2 members; Thanked: 173 times; GMAT Score:710

by gmatmachoman » Sat Jul 10, 2010 11:17 pm

phoenix9801 wrote: 2-

Mary persuaded n friends to donate $500 each to her election champaign, and then each of these n friends persuaded n more people to donate $500 each to Mary's campaign. if no one donated more than once and if there were no other donations, what was the value of n?

(1) The first n people donated 1/16 od total amount donated.

(2) the total amount donated was $120,000

First n people contribute 500 *n

n persuaded n more people : n * n * 500
= 500n ^2

St 1:
We cant much details out of it

st 2:(2) the total amount donated was $120,000
500 n^2 + 500 n = 120000
Solve for n : (15,-16)
as n is a positive number.. pick n = 15

Pick B

R&D on GMAT algorithm:

https://www.beatthegmat.com/r-d-on-gmat- ... tml#305739

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Rahul@gurome: GMAT Instructor; Posts: 1179; Joined: Sun Apr 11, 2010 9:07 pmFollowed by: 88 members; Location: Milpitas, CA; Thanked: 447 times

by Rahul@gurome » Sun Jul 11, 2010 5:00 am

phoenix9801 wrote:Hi, can someone please help to explain by step-by-step instructions (in detail) in the most simplest way and clear to understand. Would Greatly appreciate it.

1- What was the price at which a merchant sold a certain appliance?

(1) the merchant's gross profit on the appliance was 20 percent of the price at which the merchant sold the appliance.

(2) The price at which the merchant sold the appliance was $50 more than the merchant's cost of the appliance.

We know that Profit% = [(selling price - cost price)/Cost price] * 100
Let selling price = S.P, Cost price = C.P
We need to find S.P.

(1) This statement just gives profit%, which is NOT SUFFICIENT to find the S.P as we don't know the C.P.

(2) S.P = 50 + C.P. This information is also NOT SUFFICIENT as we don't know the cost price or profit%.

Combining (1) and (2), we get 20 = {[(50 + C.P) - C.P]/C.P} * 100 implies 20 = 5000/C.P or C.P = $250
So, S.P = 50 + 250 = $300
Hence, combining the statements we can answer the question.

[spoiler]The correct answer is (C).[/spoiler]

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sanabk: Master | Next Rank: 500 Posts; Posts: 174; Joined: Fri Apr 02, 2010 3:41 pmFollowed by: 1 member; Thanked: 6 times

by sanabk » Sun Jul 11, 2010 3:49 pm

Hi Rahul,

According to statement (2) The price at which the merchant sold the appliance was $50 more than the merchant's cost of the appliance.

Isn't the equation Profit% = [(selling price - cost price)/selling price] * 100 ???
In that case SP=250.

Please correct me if I am wrong.

Thanks

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Rahul@gurome: GMAT Instructor; Posts: 1179; Joined: Sun Apr 11, 2010 9:07 pmFollowed by: 88 members; Location: Milpitas, CA; Thanked: 447 times

by Rahul@gurome » Sun Jul 11, 2010 4:01 pm

sanabk wrote:Hi Rahul,

According to statement (2) The price at which the merchant sold the appliance was $50 more than the merchant's cost of the appliance.

Isn't the equation Profit% = [(selling price - cost price)/selling price] * 100 ???
In that case SP=250.

Please correct me if I am wrong.

Thanks

The formula for profit% = [(Selling Price - Cost Price)/Cost Price] * 100 because we find the profit with respect to the purchase price that is the cost price. Does that help?

Rahul Lakhani
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Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)

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phoenix9801: Master | Next Rank: 500 Posts; Posts: 190; Joined: Thu Jan 14, 2010 8:29 pm; Thanked: 2 times

by phoenix9801 » Mon Jul 12, 2010 3:21 pm

Rahul@gurome wrote:
sanabk wrote:Hi Rahul,

According to statement (2) The price at which the merchant sold the appliance was $50 more than the merchant's cost of the appliance.

Isn't the equation Profit% = [(selling price - cost price)/selling price] * 100 ???
In that case SP=250.

Please correct me if I am wrong.

Thanks
The formula for profit% = [(Selling Price - Cost Price)/Cost Price] * 100 because we find the profit with respect to the purchase price that is the cost price. Does that help?

Is there a simpler way if you can use R,C and P to make two different equations for statement 1 and 2 and how would you do it?

For example for the first statement R-C=P , but I am not sure if it is the proper way??

Last edited by phoenix9801 on Mon Jul 12, 2010 6:51 pm, edited 1 time in total.

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phoenix9801: Master | Next Rank: 500 Posts; Posts: 190; Joined: Thu Jan 14, 2010 8:29 pm; Thanked: 2 times

by phoenix9801 » Mon Jul 12, 2010 4:00 pm

gmatmachoman wrote:
phoenix9801 wrote: 2-

Mary persuaded n friends to donate $500 each to her election champaign, and then each of these n friends persuaded n more people to donate $500 each to Mary's campaign. if no one donated more than once and if there were no other donations, what was the value of n?

(1) The first n people donated 1/16 od total amount donated.

(2) the total amount donated was $120,000

First n people contribute 500 *n

n persuaded n more people : n * n * 500
= 500n ^2

St 1:
We cant much details out of it

st 2:(2) the total amount donated was $120,000
500 n^2 + 500 n = 120000
Solve for n : (15,-16)
as n is a positive number.. pick n = 15

Pick B

If the answer is B it does not make sense I though it was D. but I having trouble to come with some sort of equation to prove it. I tired to make an equation and then pick numbers somehow but not working with me. any help please..

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singhpreet1: Senior | Next Rank: 100 Posts; Posts: 95; Joined: Tue Jun 08, 2010 11:27 am; Thanked: 7 times

by singhpreet1 » Tue Jul 13, 2010 1:55 am

phoenix9801 wrote:
gmatmachoman wrote:
phoenix9801 wrote: 2-

Mary persuaded n friends to donate $500 each to her election champaign, and then each of these n friends persuaded n more people to donate $500 each to Mary's campaign. if no one donated more than once and if there were no other donations, what was the value of n?

(1) The first n people donated 1/16 od total amount donated.

(2) the total amount donated was $120,000

First n people contribute 500 *n

n persuaded n more people : n * n * 500
= 500n ^2

St 1:
We cant much details out of it

st 2:(2) the total amount donated was $120,000
500 n^2 + 500 n = 120000
Solve for n : (15,-16)
as n is a positive number.. pick n = 15

Pick B
If the answer is B it does not make sense I though it was D. but I having trouble to come with some sort of equation to prove it. I tired to make an equation and then pick numbers somehow but not working with me. any help please..

i agree with you Pheonix. it is D

im going to have a go at st. 1: 500=1/16 of the total, rest of the amount is 1-1/16=15/16.

therefore: 1/16 = 500*16=8000; therefore total is 8000*15= 120,000.

now, 120000/500=240. { also 1/16 as stated in the question}

therefore n=(15*15)+15=240. therefore n=15.

[why 15*15? each of these n friends persuaded n more people to donate $500 each to Mary's campaign. ] example: if 10 people persuade 10 people each, total will be 110(10+10*10). similarly 15 people will get 15+15 by each multiplied by 15, which is the original number of people to start with.

i know there is a better explanation but il stick to this for now till i can figure out a better one.

Preet

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sumanr84: Legendary Member; Posts: 758; Joined: Sat Aug 29, 2009 9:32 pmFollowed by: 2 members; Location: Bangalore,India; Thanked: 67 times

by sumanr84 » Tue Jul 13, 2010 2:02 am

Please use search button before posting..

https://www.beatthegmat.com/mary-persuad ... t9893.html

I am on a break !!

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