BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Arithmetic Mean(3)

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 32
Joined: Fri Feb 19, 2010 12:36 pm
Location: Pennsylvania
Thanked: 1 times

Arithmetic Mean(3)

by tsmith93 » Wed Mar 03, 2010 5:58 pm
The members of the French Club conducted a fund-raising drive. The average (arithmetic mean) amount of money raised per member was $85. Then Jean joined the club and raised $50. This lovered the average to $80. How many members were there before Jean joined?
Top
Source: — Problem Solving |
User avatar
Community Manager
Posts: 1537
Joined: Mon Aug 10, 2009 6:10 pm
Thanked: 653 times
Followed by:252 members

by papgust » Wed Mar 03, 2010 6:07 pm
Let X be the Sum of the money raised by members of french club and N be the number of members.

X / N = 85

X = 85N

X - 85N = 0 ... (1)

When Jean joined, average lowered to 80. He raised 50$,

X + 50 = 80 * (N+1)

X + 50 = 80N + 80

X - 80N = 30 ... (2)

Solving (1) and (2),

5N = 30

[spoiler]N = 6[/spoiler]
Top
Senior | Next Rank: 100 Posts
Posts: 46
Joined: Sat Feb 27, 2010 2:58 am
Location: GMAT

by GMATSUCKER » Tue Mar 16, 2010 1:55 am
IMO6. What's the OA ?
GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT, GMAT
What's life without GMAT !!!!!!!!
Top
Senior | Next Rank: 100 Posts
Posts: 43
Joined: Sat Mar 13, 2010 4:11 am
Thanked: 1 times

by STEVEN SPIELBERG » Tue Mar 16, 2010 1:57 am
What's the OA ?
I want to win an OSCAR on the GMAT !!!
Top
User avatar
Legendary Member
Posts: 526
Joined: Sat Feb 21, 2009 11:47 pm
Location: India
Thanked: 68 times
GMAT Score:680

by harshavardhanc » Tue Mar 16, 2010 3:47 am
tsmith93 wrote:The members of the French Club conducted a fund-raising drive. The average (arithmetic mean) amount of money raised per member was $85. Then Jean joined the club and raised $50. This lovered the average to $80. How many members were there before Jean joined?
Before :

The group had 85 as the avg. You can view it as n 85s i.e. 85,85,85,........n terms

After Jean joined:

the avg became 80 i.e. 80,80,80...........(n+1)terms

Even Jean is considered to have raised 80 i.e additional $30. Where did this extra amount come from.

From rest of the members. In other words, rest of the members contributed $5 each to make that extra $30.

So, how many times 5 is 30 ? :)
Regards,
Harsha
Top
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

by sanju09 » Tue Mar 16, 2010 3:59 am
tsmith93 wrote:The members of the French Club conducted a fund-raising drive. The average (arithmetic mean) amount of money raised per member was $85. Then Jean joined the club and raised $50. This lovered the average to $80. How many members were there before Jean joined?
There were x members before Jean joined, and those x must have raised $85 x already, Jean, the (x + 1)th member, raised $50 to make us write the following equation in x:

(85 x + 50) / (x + 1) = 80; solve and have

[spoiler]x = 6[/spoiler]
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
Junior | Next Rank: 30 Posts
Posts: 12
Joined: Tue Dec 29, 2009 10:21 pm

by kat187 » Wed Mar 17, 2010 10:08 pm
how do u guys come up with the solutions so fast? Is is because you have miss these one too?
Top
Post new topic Post Reply
• Page 1 of 1