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A group of marbles is arranged into x rows and y columns. If the numbe

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Math Expert
Joined: 02 Sep 2009
Posts: 58434
A group of marbles is arranged into x rows and y columns. If the numbe  [#permalink]

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21 Jan 2019, 01:10
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Difficulty:

35% (medium)

Question Stats:

71% (01:35) correct 29% (01:33) wrong based on 53 sessions

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A group of marbles is arranged into x rows and y columns. If the number of columns is 7 times the number of rows, and there are 343 total marbles, how many rows are there?

A 7
B 14
C 49
D 62
E 74

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NUS School Moderator
Joined: 18 Jul 2018
Posts: 1021
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: A group of marbles is arranged into x rows and y columns. If the numbe  [#permalink]

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21 Jan 2019, 01:23
y = 7x

Also, xy = 343
$$7x^2 = 343$$
$$x^2 = 49$$
x = +7 or -7
As x cannot be negative, x = +7
y = 49
No. of rows, x = 7.

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Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 9704
Location: Pune, India
Re: A group of marbles is arranged into x rows and y columns. If the numbe  [#permalink]

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21 Jan 2019, 03:05
Bunuel wrote:
A group of marbles is arranged into x rows and y columns. If the number of columns is 7 times the number of rows, and there are 343 total marbles, how many rows are there?

A 7
B 14
C 49
D 62
E 74

Total number of marbles = No of rows * No. of columns

343 = No of rows * 7 * No of rows (Since No of columns = 7 * No of rows)

We know that 343 = 7^3 so "No of rows" must be 7.

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Karishma
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Re: A group of marbles is arranged into x rows and y columns. If the numbe  [#permalink]

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21 Jan 2019, 08:17
Bunuel wrote:
A group of marbles is arranged into x rows and y columns. If the number of columns is 7 times the number of rows, and there are 343 total marbles, how many rows are there?

A 7
B 14
C 49
D 62
E 74

xy= 343
y=7x
7x^2 = 343
x= +/-7
IMO A
Re: A group of marbles is arranged into x rows and y columns. If the numbe   [#permalink] 21 Jan 2019, 08:17
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