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Source: — Data Sufficiency |
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by selango » Wed Jul 14, 2010 1:14 am
Vijay,

Just to know what is the source of this question?
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by kvcpk » Wed Jul 14, 2010 3:15 am
vijaynarayanan wrote:Image

Kindly help me solve.

Correct Answer: A
x-y = 9k ???

let x= 10a +b
y = 10b+a
x-y = 9(a-b)
a and b are integers. So x-y is a multiple of 9.

SUFF

x = 10a1+b1
y = 10a2+b2
a1 = b1+2
a2 = b2-2
x-y = 11b1+20 - 11b2-20
=11(b1-b2)+40
=40+11 or 40 +22 or 40+33 or 40+44 or.....
Cannot be multiple of 9

pick A
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by selango » Wed Jul 14, 2010 3:24 am
Praveen buddy.....

40+77=117 is divisible by 9.
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by kvcpk » Wed Jul 14, 2010 3:40 am
selango wrote:Praveen buddy.....

40+77=117 is divisible by 9.
Yeah you are right.. But, x and y are integers between 10 and 99.
So maximum difference among them is 99-10 =89

So x-y cannot be 117.

for x-y we will get 51, 62, 73, 84 only. Forgot to mention this in above post
None of these are divisible by 9.

Hope this helps!!
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by kvcpk » Wed Jul 14, 2010 3:47 am
oops.. Forgot the possibility that b1-b2 could be negative also.

So, 40-11, 40-22,40-33 are also possible.
-> 29,18,7
18 is divisible by 9

Hence we get conflict of YES and NO.

hence stmt2 is not sufficient.

PICK A.
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by clock60 » Wed Jul 14, 2010 12:53 pm
all is said about this problem, my answer also A and my two cents

is (x-y)/9=integer

(1) x=10a+b, y=10b+a. so
x-y=10a+b-10b-a=9a-9b=9(a-b)-must be divisible by 9
so sufficient

(2) x=10a+(a-2)=11a-2
y=10b+(b+2)=11b+2

x-y=11a-2-11b-2=11(a-b)-4, now let us check

if a-b=1, 11-4=7 not divisible by 9

a-b=2, 11*2-4=18 divisible by 9

a-b=3 11*3-4=29 not divisible by 9

as we have yes and no answers st2 insufficient
so A
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by singhpreet1 » Sat Jul 17, 2010 1:15 am
kvcpk wrote:
selango wrote:Praveen buddy.....

40+77=117 is divisible by 9.
Yeah you are right.. But, x and y are integers between 10 and 99.
So maximum difference among them is 99-10 =89

So x-y cannot be 117.

for x-y we will get 51, 62, 73, 84 only. Forgot to mention this in above post
None of these are divisible by 9.

Hope this helps!!
i beg to differ...it says that x and y are integers between 10 and 99, not that their difference is between 10 and 99. so 40+77 is a valid argument in my opinion.

Preet
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by kvcpk » Sat Jul 17, 2010 1:22 am
singhpreet1 wrote: i beg to differ...it says that x and y are integers between 10 and 99, not that their difference is between 10 and 99. so 40+77 is a valid argument in my opinion.

Preet
Hi Preet,

if x an y are integers between 10 and 99, themaximum difference x-y can be when
x is maximum and y is minimum

Maximum x possible is99, minimum y possible is 10
difrence is 99-10 = 89.

SO maximumvalue ofx-y is 89.

Hope this helps!!
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by singhpreet1 » Sat Jul 17, 2010 2:19 am
kvcpk wrote:
singhpreet1 wrote: i beg to differ...it says that x and y are integers between 10 and 99, not that their difference is between 10 and 99. so 40+77 is a valid argument in my opinion.

Preet
Hi Preet,

if x an y are integers between 10 and 99, themaximum difference x-y can be when
x is maximum and y is minimum

Maximum x possible is99, minimum y possible is 10
difrence is 99-10 = 89.

SO maximumvalue ofx-y is 89.

Hope this helps!!
that is true...i need to convince myself to do the maximum- minimum concept to get this straight.

thanks.

Preet
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