Please help

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wind612: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Sat Apr 23, 2011 7:58 pm

by wind612 » Sun Apr 24, 2011 8:59 am

1. A thin conveyor belt 15 feet long is drawn tightly around two circular wheels each 1 foot in diameter. What is the distance, in feer between the centers of the two wheels?
2. In a survey of students, each student selected from a list of 12 songs the 2 songs that the student liked best. If each song was selected 4 times, how many students were surveyed?
3. In the xy-coordinate plane, line l and line k intersect at one point (4,3). Is the product of their slope negative?
1)The product of the x-intercept of line l and k is positive
2) The product of the y-intercept of line l and k is negative

Your help will be greatly appreciated!!

Source: Beat The GMAT — Problem Solving | Sun Apr 24, 2011 8:59 am

vineeshp: Legendary Member; Posts: 965; Joined: Thu Jan 28, 2010 12:52 amFollowed by: 34 members; Thanked: 156 times; GMAT Score:720

by vineeshp » Sun Apr 24, 2011 10:05 am

1. A total length of 15 is wound around 2 circles near each other.

Pi*r + 2*L + Pi*r = 15

Pi*1/2 + 2*L + Pi*1/2 = 15
L= (15 - pi)/2

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Last edited by vineeshp on Sun Apr 24, 2011 8:16 pm, edited 1 time in total.

Vineesh,
Just telling you what I know and think. I am not the expert.

wind612: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Sat Apr 23, 2011 7:58 pm

by wind612 » Sun Apr 24, 2011 12:22 pm

Thanks for your reply! But I dont know why the answer for it was (15 - Pi)/2

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Sun Apr 24, 2011 6:59 pm

vineeshp wrote:1. A total length of 15 is wound around 2 circles near each other.

Pi*r + 2*L + Pi*r = 15

Pi*1 + 2*L + Pi*1 = 15
L= (15 - 2 * pi)/2

The diameter = 1.
So, radius = 1/2.
Or, pi*1/2 + 2*L + pi*1/2 = 15.
Or L = (15 - pi)/2.

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Sun Apr 24, 2011 7:35 pm

2. In a survey of students, each student selected from a list of 12 songs the 2 songs that the student liked best. If each song was selected 4 times, how many students were surveyed?

Solution:
If each song was selected 4 times, then in total, 12*4 = 48 selections were made.
Now, each student is selecting 2 songs.
So, total number of students surveyed is 48/2 = 24.

vineeshp: Legendary Member; Posts: 965; Joined: Thu Jan 28, 2010 12:52 amFollowed by: 34 members; Thanked: 156 times; GMAT Score:720

by vineeshp » Sun Apr 24, 2011 8:17 pm

Anurag@Gurome wrote:
The diameter = 1.
So, radius = 1/2.
Or, pi*1/2 + 2*L + pi*1/2 = 15.
Or L = (15 - pi)/2.

Thanks a lot, Anurag. Careless me! Now I know why I dont hit 50 in quant on my tests. :-/

Vineesh,
Just telling you what I know and think. I am not the expert.

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