GMAT Question of the Day : Data Sufficiency

Killer
#1. July 27th, 2006, at 7:22 PM.

12

Krishna Mohan
#2. July 27th, 2006, at 7:35 PM.

D. 18

Rao
#3. July 27th, 2006, at 8:26 PM.

its D - 18

I read problem as (x/(x+y))(10)+(y/(x+y))(20)=K
to make K integer x+y should be multiple 5 or 10
possible values for x and y are
(1,4)(2,3)(1,9)(2,8)(3,7)(4,6)

we don’t need to solve all of this.. first try (1,4) u get 18.. thas it !!
we need not have to waste time prooving other options can be values of K

Krishna Mohan
#4. July 27th, 2006, at 9:45 PM.

Here is how i solved this problem.
Equation is 10+10(y/x+y) and as x

Krishna Mohan
#5. July 27th, 2006, at 9:46 PM.

Didn’t display the whole part…..
Here is how i solved this problem.
Equation is 10+10(y/x+y) and as x

Milind
#6. July 28th, 2006, at 9:31 PM.

Yes, its D

your equation becomes
10(x+2y)/(x+y) = k
=> (x+2y)/(x+y) = k/10

The only number to satisfy this is 18. Its doesn’t take long cause you always start from the center value, in this case 15 and then increase / decrease the value based on your first answer.

pal
#7. March 25th, 2007, at 1:04 PM.

D…gud question..

sumanth toom
#8. March 25th, 2008, at 4:22 PM.

D.
(x/(x+y)) (10) + (y/(x+y)) (20)
= (x/(x+y)) (10) + (y/(x+y)) * 10 + (y/(x+y)) * 10
= 10 [x/(x+y) + y/(x+y)] + (y/(x+y)) * 10
= 10 [1] + 10y/(x+y)

clearly k should be > 10. And y/(x+y) is 10 A

say y/(y+x) = q,
y = qx + qy
y(1-q) = qx
y/x = q/(1-q),
since y > x, y/x = q/(1-q) > 1
==> q > 1 - q
==> 2q > 1
==> q > 0.5

Using A, here q (which is y/(y+x) ) can be .6,.7, .8 or .9 only.
i.e, the ans can be 16, 17, 18, 19. …
only option avaliable: 18 : D.
phew !!

john
#9. March 26th, 2008, at 2:07 PM.

if x = y, then k = 15.

if x 15

but then k would never exceed 20, as 20 is like the plateu.
therefore k is bounded between 15 and 20.

the only good option is 18.

the answer is D

Vamsi Krishna Kanuri
#10. August 21st, 2008, at 9:32 AM.

D

Reasoning :

on minimizing the equation, we get 10+[(10)(y/(x+y)] = K

Since, the answer choices are all integers, 10y when divided by (x+y) should yield an integer. Therefore, look for pairs of (x,y) which sum to either 5 or 10. By trial and error methods, substituting (x,y) = (1,4), we get K = 18

Jagadeesh Pala
#11. August 21st, 2008, at 10:11 AM.

Good Approach sumanth toom.

Rao… Your reasoning is flawed with your statement
“to make K integer x+y should be multiple 5 or 10″

(x/(x+y))(10)+(y/(x+y))(20)=K
It was never said that K is an integer and even if it was said said that K is an
integer x+y can be 1, 2 , 5 , 10 and depends on values of x and y also.

Lalit
#12. August 22nd, 2008, at 12:54 AM.

Simplfying the equation as 10x/(x+y) + 10y/(x+y) + 10y/(x+y) = K
x (x + y) < 2y or 5(x+y) < 10y

so 10 + 10y /(x+y) will be less than 10 + 5(x+y)/(x+y)

Hence from ans options its “12″.

Manian
#13. August 22nd, 2008, at 5:30 PM.

10x/(x+y) +20y/(x+y) = k

10x+20y/(x+y) = k
10x+20y= kx+ky
(10-k)x+(20-k)y =0

and x y and 30 will yeild both x component and y
component to negative which never going to make zero.
only option remaing 18 . which can yeild -8x+2y = 0
I think 18 is the possible answer

arpita
#14. August 22nd, 2008, at 11:02 PM.

a

vars
#15. August 23rd, 2008, at 12:20 AM.

firstly this is not a DS ques. n the correct answer is not listed here. let me show how.

the equation comes down to 10 + 10(1/(x/y)+1) = k
since x/y<1 and we are not given with the exact value , then x/y can vary from 0.1to 0.9 putting this in equation we get 18.3 and 19.1 among the answers. So this question does not really make sense to me

indomitable18
#16. August 26th, 2008, at 11:51 AM.

since its mentioned x<y. So alets take x=2and y=3 and put it in the equation.

then we get k=16
thus the choice left is only 18 so simple.