prep question

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prep question

by jamesk486 » Thu Apr 19, 2007 12:14 am
A, b and c are 3 digit positive integers, where a=b+c. Is the hundreds digit of A equal to the sum of the hundreds digit of b and the hundredes digit of c?
(1) the tens digit of A is equal to the sum of the tens digit of b and the tens digit of c
(2) the units digit of a is equal to the sum of the units digit of b and the units digit of c.

For (1), b=542, c=351, so a= 893
but then the tens digits of b and c can both be 5 so a can't be a 3 digit ineger
(2) is insufficient==> b=545, c=455, so then a would be 1000

but why is the answer A??

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Re: prep question

by Prasanna » Thu Apr 19, 2007 8:26 pm
jamesk486 wrote:A, b and c are 3 digit positive integers, where a=b+c. Is the hundreds digit of A equal to the sum of the hundreds digit of b and the hundredes digit of c?
(1) the tens digit of A is equal to the sum of the tens digit of b and the tens digit of c
(2) the units digit of a is equal to the sum of the units digit of b and the units digit of c.

For (1), b=542, c=351, so a= 893
but then the tens digits of b and c can both be 5 so a can't be a 3 digit ineger
(2) is insufficient==> b=545, c=455, so then a would be 1000

but why is the answer A??
Hi

When you assign the value of 5 to tens digit in both b and c, condition(1) is not satisified. In this case tens digit in A would be zero. Hence we cannot check for that set of values. The answer would be A.

The question states that a, b and c are all three digit positive integers and condition (1) is sufficient to answer the question.