GMAT Data Sufficiency Discussions

MBA GMAT
1261
Few more....

2. If w and c are integers, is w > 0?
(1) w + c > 50
(2) c > 48


St 1 : no clue abt c, hence cannot predict abt w ...not suff

St 2: only tells about x, caanot say about w ...not suff

Combined : still tells us nothing , as w can be +ve or -ve
eg c=49 and w =2
Or c = 60 and w = -5 ,,

Ans E
1262
Yesterday Diana spent a total of 240 minutes attending a training class, responding to Emails, and talking on the phone. If she did no two of these three activities at the same time, how much time did she spend talking on the phone?


(1) Yesterday the amount of time that Diana spent attending the training class was 90 percent of the amount of time that she spent responding to E-mails.
(2) Yesterday the amount of time that Diana spent attending the training class was 60 percent of the total amount of time that she spent responding to E-mails and talking on the phone.


tri variate ..we need 3 independent equations
Let E-mail = E ; training class = C; phone =P


St 1 : If E = x then T = 0.9x : P = 240 -1.9x ..just 1 more eq ..not suff

St 2 : gives u only 1 eq ...not suff

Combined : 0.9x = 0.6 (x + 240 - 1.9x)...linear eqn in X ...suff ..
we can get all corr values ...

Ans C
1263
What is the cube root of
w ?

(1) The 5th root of
w is 64.
(2) The 15th root of w is 4.
the OA is option B.. how come..??..


i tink ...ans sud be (D)
1264
What is the cube root of
w ?

(1) The 5th root of
w is 64.
(2) The 15th root of w is 4.
the OA is option B.. how come..??..


I think the answer should be D ..

1265
tri variate ..we need 3 independent equations
Let E-mail = E ; training class = C; phone =P


St 1 : If E = x then T = 0.9x : P = 240 -1.9x ..just 1 more eq ..not suff

St 2 : gives u only 1 eq ...not suff

Combined : 0.9x = 0.6 (x + 240 - 1.9x)...linear eqn in X ...suff ..
we can get all corr values ...

Ans C


I also marked option C only.. but OA seems to be D.. I am utterly confused, bcoz stmt 1 cannot be used to solve this..

u wanna try again and see if option D can be the answer..
1266

so wats the final take on this one.. option C or option E

well.. for me it goes something like..

option1:
possibly X is +ve or -ve..
and
for sure X
ZERO

option2:
possible X is zero or -ve
and
for sure X
+ve

combining 2 we get..for sure X
ZERO and for sure X
+ve

thus answer can be reached with the help of both statements...

remember this is a YES/NO answer..and using the statement provided the answer can be reached, i.e. YES.

my asnwer choice still remains option C ;)

well..

St 1 : x is +ve or -ve
St 2: x. Y is not a positive number implies product is 0 or -ve

possibilities:
a) X=0 and Y is any no
OR
b) x= any real no and y = 0
OR
c) x= -ve and y = any no

combined statements :

It tells us x is not zero ...so option a) of St 2 is gone ...
But still we cannot rule out option b and c of statement 2 ..

Or in other words, x can be any real no (which includes positive no) Or -ve ..still no concensus whether x is -ve ...

Hence E ..

I guess this should be correct
1267
I also marked option C only.. but OA seems to be D.. I am utterly confused, bcoz stmt 1 cannot be used to solve this..

u wanna try again and see if option D can be the answer..


did give it a thought again ...D simply is not poss

We know total of 3 is 240

St 1 : email is x and class is 0.9x , thats all, phone would depend on the value of x which is variable ,,,not suff ..

Ans should be C only !!
1268
well.. for me it goes something like..

option1:
possibly X is +ve or -ve..
and
for sure X
ZERO

option2:
possible X is zero or -ve
and
for sure X
+ve

combining 2 we get..for sure X
ZERO and for sure X +ve

thus answer can be reached with the help of both statements...

remember this is a YES/NO answer..and using the statement provided the answer can be reached, i.e. YES.

my asnwer choice still remains option C ;)

nuttyvarun Says
so wats the final take on this one.. option C or option E


he he ...i thought i had posted back ...serious connectivity issues on my end :(

well, am not really sure what u wanted to convey thru bold statement ...but i guess u meant x is a non zero number i.e it can be positive or negative ..

And yes, we do do not need a definite value, but a definite yes that x is =ve OR a definite no that x is non negative ..

Since x can either be positive or negative, there is no definite stance, and hence insufficient ..

I maintain my Ans as E ..

I guess lets wait for OA before somebody groans for spamming
1269

humm.. seems ur internet conn sux as much as my maths

btw referring to the highlighted section in ur post below.. I think both statements ensure that its not zero and positive.. so u r not left with any other option but negative..

anyway.. guess we both would have to wait till the OA is disclosed.. ;)

he he ...i thought i had posted back ...serious connectivity issues on my end :(

well, am not really sure what u wanted to convey thru bold statement ...but i guess u meant x is a non zero number i.e it can be positive or negative ..

And yes, we do do not need a definite value, but a definite yes that x is =ve OR a definite no that x is non negative ..

Since x can either be positive or negative, there is no definite stance, and hence insufficient ..

I maintain my Ans as E ..

I guess lets wait for OA before somebody groans for spamming
1270
What is the cube root of
w ?
(1) The 5th root of w is 64.

(2) The 15th root of w is 4.
the OA is option B.. how come..??..


is it D? 😞
1271
Mcnabb_ISB Says
is it D? :(


x/3=5*x/15
taking cos and sin of both sides-
cosx/3+i sinx/3=cos5*x/15+i sin 5*x/15
=(cosx/15+i sinx/15)^5
=4^5

hence answer is B only.
here 5 can be taken as power bcoz its an integer.
1272
Yesterday Diana spent a total of 240 minutes attending a training class, responding to Emails, and talking on the phone. If she did no two of these three activities at the same time, how much time did she spend talking on the phone?


(1) Yesterday the amount of time that Diana spent attending the training class was 90 percent of the amount of time that she spent responding to E-mails.
(2) Yesterday the amount of time that Diana spent attending the training class was 60 percent of the total amount of time that she spent responding to E-mails and talking on the phone.


The answer is C.
1273
What is the cube root of
w ?

(1) The 5th root of
w is 64.
(2) The 15th root of w is 4.
the OA is option B.. how come..??..

x/3=5*x/15
taking cos and sin of both sides-
cosx/3+i sinx/3=cos5*x/15+i sin 5*x/15
=(cosx/15+i sinx/15)^5
=4^5

hence answer is B only.
here 5 can be taken as power bcoz its an integer.


Then for that matter even st 1 is sufficient ..

we need w^1/3 ?

st 1 : w^1/5 = 64 i.e w= 64^5 = 2^30 hence cube root is 2^10

St 2 : w^1/15 = 4 i.e w = 4^15 = 2^30 hence cube root is 2^10

I am banking on the fact that every positive real number has a single positive nth root ..

So, my answer is D ..

Can somebody throw some light, why B only ?
@gutsy : even using trigo (though not expected on GMAT) how did u rule out St 1 ?

1274
Then for that matter even st 1 is sufficient ..

we need w^1/3 ?

st 1 : w^1/5 = 64 i.e w= 64^5 = 2^30 hence cube root is 2^10

St 2 : w^1/15 = 4 i.e w = 4^15 = 2^30 hence cube root is 2^10

I am banking on the fact that every positive real number has a single positive nth root ..

So, my answer is D ..

Can somebody throw some light, why B only ?
@gutsy : even using trigo (though not expected on GMAT) how did u rule out St 1 ?



bcoz x/3=(5/3)*x/5=>5/3 is an integer so it cant be taken to the power of expression.
This is about Demoivers theorem of complex algebra.
I also feel this is otside the scope of GMAT.
Yours approach is definately correct if you take real numbers only.and D will be the answer
if you take complex also in case,B is the only choice.
1275
bcoz x/3=(5/3)*x/5=>5/3 is an integer so it cant be taken to the power of expression.
This is about Demoivers theorem of complex algebra.
I also feel this is otside the scope of GMAT.
Yours approach is definately correct if you take real numbers only.and D will be the answer
if you take complex also in case,B is the only choice.


Thanx for the pointer buddy !! Learnt about Demoivers theorem today ..
Yes, complex nos is not a part of GMAT !! real nos only !!
1276
Few more....
1. If x and y are positive, is 3x > 7y?
(1) x > y + 4
(2) -5x
2. If w and c are integers, is w > 0?
(1) w + c > 50
(2) c > 48



1) IMO B is the answer.

Take 1) here if y=0.1 then x=4.1
so 3x>7y. but if y=100 then x =105 and 3x!> 7y. so A alone is not suff.

Take 2) 5x>14y
.35x>y so .42x is definitely greater than y.

Hence B.

2) E.
Take 1) 2 unknows and 1 equation. So not suff.

take 2) C>48 so w can be 1,0,-1 and so on. so not suff.

take both, still here we have no clarity on w and c. hence E
1277

x is a positive integer, is the remainder 0 when 3^x + 1 is divided by 10?

1> x = 4n + 2
2> x>4

1278

Is the positive integer N a perfect square?

(1) The number of distinct factors of N is even.
(2) The sum of all distinct factors of N is even.

1279

If x and y are nonzero integers, is x^y > y^x?
(1) x = y2
(2) y > 2

1280
Is the positive integer N a perfect square?

(1) The number of distinct factors of N is even.
(2) The sum of all distinct factors of N is even.


Good conceptual question !!

Ans D

Perfect square always has an odd no of factors whose sum is also always odd ..

If required can post the proof for the same as well ..