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If r is the remainder

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Source: — Data Sufficiency |
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by ssmiles08 » Fri Aug 07, 2009 5:24 pm
N = 7Q + R. Find R. R can be any positive digit less than 7.

1) n = 21S + O. Insufficient b/c O can has many odd numbers less than 21.

2) n = 28P + 3

set both equations equal to each other; 7Q + R = 28P + 3

7Q - 28P = R + 3

7(Q - 4P) = R + 3

(Q - 4P) = (R + 3)/7

R is a positive integer less than 7.

R is 4. Sufficient

IMO B.
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by alexdallas » Fri Aug 07, 2009 5:27 pm
OA is B by the way.
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by alexdallas » Fri Aug 07, 2009 5:30 pm
i dont get this part:

"(Q - 4P) = (R + 3)/7

R is a positive integer less than 7.

R is 4. Sufficient "

can u pls elaborate?
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by tarun'susername » Sat Aug 08, 2009 3:59 am
The answer is B,
Here is my explaination:

B mentions-when the number is divided by 28, remainder is 3. so the number can be represented by 28x +3, where x can be any positive interger.
Now when you divide 28x+3 by 7, since 28 is divisible by 7 , thus 28x is divisible by 7, and thus the remainder will be 3. e.g. 31/7=3 or 59/7=3
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