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Sum of digits

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by goelmohit2002 » Thu Aug 20, 2009 11:08 am
A,B and C are 3 digit integers, where A = B + C. Is the hundreds' digit of number A equal to sum of hundreds' digit of B and C ?
1) Tens' digit of A = Tens' digit of B + Tens' digit of C
2) Units' digit of A = Units' digit of B + Units' digit of C

OA = After some discussion.
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Source: — Data Sufficiency |
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by pandeyvineet24 » Thu Aug 20, 2009 11:51 am
Should be A.

Stmt 1

a = b + c.

(1)) Tens' digit of A = Tens' digit of B + Tens' digit of C
this means that sum of tens digit of b and tens digit of c should be less than 10.Interestingly, this also forces that sum of unit digits should be less than 10.
That being the case, the hunderedth digit of a will always be equal to hundered digits of b and c
do few ex.

b = 235, c= 543 a = 778

b = 587, c = 332, a = 919 - sum of tens digit of b and tens digit of c not less than 10.

b = 154, c = 255 a= 409 - sum of tens digit of b and tens digit of c not less than 10.

sueff,


Stmt 2
not sueff

try different combinations.

b= 103, c = 203 a = 306. works

b= 153, c = 253 a = 406. does not work
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by goelmohit2002 » Fri Aug 21, 2009 8:53 am
Here OA = E....

I am not sure how....

can someone please tell how E is correct ?
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by quant-master » Fri Aug 21, 2009 9:24 am
goelmohit2002 wrote:Here OA = E....

I am not sure how....

can someone please tell how E is correct ?
I guess OA is wrong.

Thanks,
Quant-Master
https://gmat-quants.blocked - My Blog Updated almost daily with new quant fundas. Find collection of quants question in my blog
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by scoobydooby » Fri Aug 21, 2009 9:27 am
am getting A as well.
what is the source?
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by goelmohit2002 » Fri Aug 21, 2009 9:27 am
Thanks all. I too was puzzled by the OA...

I guess the correct answer should be A.
Last edited by goelmohit2002 on Fri Aug 28, 2009 11:11 am, edited 1 time in total.
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by goelmohit2002 » Fri Aug 21, 2009 9:31 am
scoobydooby wrote:am getting A as well.
what is the source?
One of my friends who is studying in a reputed GMAT coaching institute gave me this question.....his class assignment had this question.
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by woo » Fri Aug 21, 2009 11:06 pm
I have not thought about it enough

but it may be because the numbers can be negative

numbers?
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by goelmohit2002 » Fri Aug 21, 2009 11:37 pm
woo wrote:I have not thought about it enough

but it may be because the numbers can be negative

numbers?
Thanks woo....good point !!!

Can you please illustrate how does -ve numbers will impact the answer ?
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by pradeepsarathy » Thu Aug 27, 2009 7:24 pm
IMO E


Stmt 1:

Tens' digit of A = Tens' digit of B + Tens' digit of C

Insufficient - This does not talk about the hundreth digit

Case 1:

B = 123, C = 321, A = 444

123 + 321 = 444 ------> This eqn satisfies the stmt 1 and also, from this we can conclude that the hundreth digit of A is equal to hundreth digit of B + hundreth digit of C

Case 2:

B = 523, C = 532, A = 1055

523 + 532 = 1055 -----> This eqn satisfies the stmt 1 but the hundreth digit of A is not equal to hundreth digit of B + hundreth digit of C

Hence stmt 1 alone is insufficient

Stmts 2:

Units' digit of A = Units' digit of B + Units' digit of C

Two cases - same as above .

Hence stmt 2 is also not sufficient

Combining both stmt 1 and stmt 2:

Two cases - same as above .

We cannot conclude whether the hundreth digit of A is equal to the hundreth digit of B + hundreth digit of C

Hence Insufficient.
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by tohellandback » Thu Aug 27, 2009 8:58 pm
pradeepsarathy wrote:IMO E


Stmt 1:

Tens' digit of A = Tens' digit of B + Tens' digit of C

Insufficient - This does not talk about the hundreth digit

Case 1:

B = 123, C = 321, A = 444

123 + 321 = 444 ------> This eqn satisfies the stmt 1 and also, from this we can conclude that the hundreth digit of A is equal to hundreth digit of B + hundreth digit of C

Case 2:

B = 523, C = 532, A = 1055

523 + 532 = 1055 -----> This eqn satisfies the stmt 1 but the hundreth digit of A is not equal to hundreth digit of B + hundreth digit of C

Hence stmt 1 alone is insufficient

Stmts 2:

Units' digit of A = Units' digit of B + Units' digit of C

Two cases - same as above .

Hence stmt 2 is also not sufficient

Combining both stmt 1 and stmt 2:

Two cases - same as above .

We cannot conclude whether the hundreth digit of A is equal to the hundreth digit of B + hundreth digit of C

Hence Insufficient.
In your Case 2 for statement 1:
integer A 1055 is a 4 digit integer which you cannot assume because question stem says that A is a 3 -digit integer.
Answer IMO is A
The powers of two are bloody impolite!!
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by goelmohit2002 » Thu Aug 27, 2009 9:00 pm
pradeepsarathy wrote:IMO E


Stmt 1:

Tens' digit of A = Tens' digit of B + Tens' digit of C

Insufficient - This does not talk about the hundreth digit

Case 1:

B = 123, C = 321, A = 444

123 + 321 = 444 ------> This eqn satisfies the stmt 1 and also, from this we can conclude that the hundreth digit of A is equal to hundreth digit of B + hundreth digit of C

Case 2:

B = 523, C = 532, A = 1055

523 + 532 = 1055 -----> This eqn satisfies the stmt 1 but the hundreth digit of A is not equal to hundreth digit of B + hundreth digit of C

Hence stmt 1 alone is insufficient
Please note that A cannot be 1055...as it is given to be 3 digit integer.
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Re: Sum of digits

by vikram_k51 » Thu Aug 27, 2009 11:24 pm
goelmohit2002 wrote:A,B and C are 3 digit integers, where A = B + C. Is the hundreds' digit of number A equal to sum of hundreds' digit of B and C ?
1) Tens' digit of A = Tens' digit of B + Tens' digit of C
2) Units' digit of A = Units' digit of B + Units' digit of C

OA = After some discussion.
Think it will be A
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by pradeepsarathy » Fri Aug 28, 2009 5:19 am
shoot...
my bad...missed that part...
yep i agree...i revise my IMO. It's A.
Thanks tohellandback for pointing it out.
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