Defined functions

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anhe123: Junior | Next Rank: 30 Posts; Posts: 21; Joined: Fri Aug 06, 2010 1:30 am

by anhe123 » Thu Sep 30, 2010 6:27 am

If A*B is the greatest common factor of A and B, A$B is defined as the least common multiple of A
and B, and (A intersection B) is defined as equal to (A*B) $ (A$B), then what is the value of (12 intersection 15)?

How would you solve this? Are there any tips you have for solvning defined functions?[/list]

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Source: Beat The GMAT — Problem Solving | Thu Sep 30, 2010 6:27 am

kmittal82: Master | Next Rank: 500 Posts; Posts: 324; Joined: Mon Jul 05, 2010 6:44 amFollowed by: 3 members; Location: London; Thanked: 70 times

by kmittal82 » Thu Sep 30, 2010 6:40 am

First you need to expand each of the brackets:

(A*B) = (12*15) = 3 (3 is the greatest common factor of 12 and 15)
(A$B) = (12$15) = 60 (60 is the least common multiple of 12 and 15)

>(A*B) $ (A$B),

= 3 $ 60 = Least common multiple of 3 and 60 = 60

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anhe123: Junior | Next Rank: 30 Posts; Posts: 21; Joined: Fri Aug 06, 2010 1:30 am

by anhe123 » Thu Sep 30, 2010 6:43 am

kmittal82 wrote:First you need to expand each of the brackets:

(A*B) = (12*15) = 3 (3 is the greatest common factor of 12 and 15)
(A$B) = (12$15) = 60 (60 is the least common multiple of 12 and 15)

>(A*B) $ (A$B),

= 3 $ 60 = Least common multiple of 3 and 60 = 60

But what does the dollar sign ($) mean?

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shovan85: Community Manager; Posts: 991; Joined: Thu Sep 23, 2010 6:19 amFollowed by: 24 members; Location: Bangalore, India; Thanked: 146 times

by shovan85 » Thu Sep 30, 2010 6:44 am

IMO 60

Break the whole expression.
Solve the bracketed individually.
Merge the answers of bracketed to the single expression.

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kmittal82: Master | Next Rank: 500 Posts; Posts: 324; Joined: Mon Jul 05, 2010 6:44 amFollowed by: 3 members; Location: London; Thanked: 70 times

by kmittal82 » Thu Sep 30, 2010 6:52 am

andre.heggli wrote:
kmittal82 wrote:First you need to expand each of the brackets:

(A*B) = (12*15) = 3 (3 is the greatest common factor of 12 and 15)
(A$B) = (12$15) = 60 (60 is the least common multiple of 12 and 15)

>(A*B) $ (A$B),

= 3 $ 60 = Least common multiple of 3 and 60 = 60

But what does the dollar sign ($) mean?

Nothing, its just a symbol to represent a mathematical operation... you can replace it with whatever you like.

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