document.write( "Question 32117: Students of a class are made to stand in rows . If 4 students are extra in a row , there would be two rows less . If 4 students are less in a row , there would be 4 more rows . Find the number of students in the class ?
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Algebra.Com's Answer #18636 by Paul(988) $\"\"$ $\"About$

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Let the number of students in each row be x, and the number of rows be y.
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document.write( "xy = (x + 4)(y – 2) 
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document.write( "xy = (x – 4)(y + 4)
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document.write( "From xy = (x + 4)(y – 2):
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document.write( "xy = xy – 2x + 4y – 8
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document.write( "xy – xy = xy – 2x + 4y – 8 – xy
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document.write( "0 = -2x + 4y – 8
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document.write( "0 = x – 2y + 4
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document.write( "x – 2y + 4 – 4 = 0 – 4
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document.write( "x – 2y = -4
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document.write( "From xy = (x – 4)(y + 4):
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document.write( "xy = xy + 4x – 4y – 16
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document.write( "xy – xy = xy + 4x – 4y – 16 – xy
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document.write( "0 = 4x – 4y – 16
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document.write( "0 = x – y – 4
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document.write( "x – y – 4 + y + 4 = 0 + y + 4
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document.write( "x = y + 4
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document.write( "Substitute x = y + 4 into x – 2y = -4:
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document.write( "y + 4 – 2y = -4
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document.write( "-y + 4 = -4
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document.write( "-y + 4 – 4 = -4 – 4
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document.write( "-y = -8
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document.write( "y = 8
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document.write( "Substitute y = 8 into x = y + 4:
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document.write( "x = 8 + 4
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document.write( "x = 12
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document.write( "xy = (12)(8) = 96
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document.write( "Hence, the number of students is 96.\r
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document.write( "Paul.
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