GMAT Data Sufficiency Discussions

siddharthaduggirala · August 6, 2009, 3:49pm

You both got it right.. though you are far away from OA, but I am convinced this is right answer

I got this wrong.. I opted for option D, but forgot to notice that n=0 along with n=-10 in option 2.. :(

thanks buddies.. ;)

Whats the OA? Post the OA any way so that we know.

nuttyvarun · August 6, 2009, 4:33pm

siddharthaduggirala Says
Whats the OA? Post the OA any way so that we know.

OA is/was option C

siddharthaduggirala · August 7, 2009, 2:40am

nuttyvarun Says
OA is/was option C

Hey, this ans must be incorrect. Whats the source?

pj02 · August 7, 2009, 4:03am

Is the measure of one of the interior angles of quadrilateral ABCD equal to 60 degrees?

(1) Two of the interior angles of ABCD are right angles.
(2) The degree measure of angle ABC is twice the degree measure of angle BCD.
Ans: Edited :biggrin:

Answer should be C. Both together are sufficient.

Approach:

1. Two interier angles at right angle. -- not sufficient

2.The degree measure of angle ABC is twice the degree measure of angle BCD-- not sufficient.

No together:
A + B+C+D=360
90+x+2x+90=360
x=60 and 2x=120.

This proves !!!

pj02 · August 7, 2009, 4:06am

Varun - As usual, a fantastic question.

IMO: Option E Both 1 and 2 are not Suff

1. 2 interior angles at 90, so sum of the other two is 180 as A+B+C+D = 360.
Sum being 180, one possibility is to have one of the angles at 60, but there are other options. So NOT SUFF

2. Angle B = 2* Angle C so, A+2C+C+D = 360. By itself this takes us no where. So, NOT SUFF

1 & 2 Together: If A and D (lets say) are the angles = 90, then we can have 3C = 180, so C=60.
But this is only one scenario.
We can also have 90,90,45,135. That suffices both the conditions of 1 and 2. two interior angles at 90 each, and one angle is twice the other (B=2C).

So Together, NOT SUFF.
Answer is E.

Vikram....
How can we have 45 and 135 as two angles? 135= 3 * 45

One angle should be double of the other and not Triple.

guy_with_guts · August 7, 2009, 4:19am

Answer should be C. Both together are sufficient.
Approach:
1. Two interier angles at right angle. -- not sufficient
2.The degree measure of angle ABC is twice the degree measure of angle BCD-- not sufficient.
No together:
A + B+C+D=360
90+x+2x+90=360
x=60 and 2x=120.
This proves !!!

can you tell me if two interior angles are 90 degrees y the other two will not be 90?as per me all are 90 so suffecient.
from second we cant say anythng unless regular can be used

guy_with_guts · August 7, 2009, 4:28am

@guy with guts
I like your conviction, "So Answer has to be A".. but unfortunately.. thats the wrong answer..

infact if you would notice option 2 closely (Train Q averaged a speed of 55 miles per hour for the entire trip) you would see that the speed of train Q remains constant througout the trip.. so you know the distance covered by Q each hour..

so in 2 hours Q would cover 55x2 = 110
in 2 hours Q meets P, so P has covered 250-110=140

so u know clearly that P is closer to its final destination..
option 2 is suff

coming back to option 1, "At the time when the two trains passed, train P had averaged a speed of 70 miles per hour." This means that train P has covered 70x2=140 at th etime it met train Q

thus Q must have travelled 250-140=110

so again u know that P is closer to its final destination..
option 1 is suff

the answer must be option D

hope that helps!! ;)

NOPE.I will not buy that idea.the term average itself means that its not constant but its an average over a period of time.yours entire approach is based on the last two term-entire trip.
Option has to be A.
BTW C can not be the answer

pj02 · August 7, 2009, 4:44am

can you tell me if two interior angles are 90 degrees y the other two will not be 90?as per me all are 90 so suffecient.
from second we cant say anythng unless regular can be used

Why other two will be 90?

We know one is 2 times the other. So its 60 and 120 thats the ONLY possibilility.

pj02 · August 7, 2009, 4:54am

@guy with guts
I like your conviction, "So Answer has to be A".. but unfortunately.. thats the wrong answer..

infact if you would notice option 2 closely (Train Q averaged a speed of 55 miles per hour for the entire trip) you would see that the speed of train Q remains constant througout the trip.. so you know the distance covered by Q each hour..

so in 2 hours Q would cover 55x2 = 110
in 2 hours Q meets P, so P has covered 250-110=140

so u know clearly that P is closer to its final destination..
option 2 is suff

coming back to option 1, "At the time when the two trains passed, train P had averaged a speed of 70 miles per hour." This means that train P has covered 70x2=140 at th etime it met train Q

thus Q must have travelled 250-140=110

so again u know that P is closer to its final destination..
option 1 is suff

the answer must be option D

hope that helps!! ;)

Guys with guts is corect. Options should be A.

2nd statement is useless as its not talking anything abt speed when the trains meet. You never know what speed might be till that time.

Please note: Speed of Q is not constant throughout and its NOT possible to calculate distance travelled by it every hour.

Answer should be A.

guy_with_guts · August 7, 2009, 5:45am

Why other two will be 90?

We know one is 2 times the other. So its 60 and 120 thats the ONLY possibilility.

NO dear , i am saying why choice A alone is not suffecient.When we know two angles are 90 , arn't the other two will be 90?
I tried to make a quadrilateral with two angles as 90 and other two different but................

bhavin422 · August 7, 2009, 6:32am

Vikram....
How can we have 45 and 135 as two angles? 135= 3 * 45
One angle should be double of the other and not Triple.

Hey pj02, Vikram's explanation for quadrilateral sum is perfect ...to satisfy the second condition of one angle being twice the other, no where has it been mentioned it is applicable to non right angles only..
so for 90-90-45-135 satisfies because 90 is twice of 45 and has nothing to do with 45 and 135

NO dear , i am saying why choice A alone is not suffecient.When we know two angles are 90 , arn't the other two will be 90?
I tried to make a quadrilateral with two angles as 90 and other two different but................

If 2 angles are 90 in a quadrilateral, it does not imply other 2 are 90 as well...
I am sure u will be able to do it , else, draw a C, 2 edges are rt angles and stretch the lower or upper arm and join the slant line. other 2 are not 90 degrees

Ans E

vyomb · August 7, 2009, 7:10am

Originally Posted by nuttyvarun View Post
@guy with guts
I like your conviction, "So Answer has to be A".. but unfortunately.. thats the wrong answer..
infact if you would notice option 2 closely (Train Q averaged a speed of 55 miles per hour for the entire trip) you would see that the speed of train Q remains constant througout the trip.. so you know the distance covered by Q each hour..
so in 2 hours Q would cover 55x2 = 110
in 2 hours Q meets P, so P has covered 250-110=140
so u know clearly that P is closer to its final destination..
option 2 is suff
coming back to option 1, "At the time when the two trains passed, train P had averaged a speed of 70 miles per hour." This means that train P has covered 70x2=140 at th etime it met train Q
thus Q must have travelled 250-140=110
so again u know that P is closer to its final destination..
option 1 is suff
the answer must be option D
hope that helps!!

Guys with guts is corect. Options should be A.
2nd statement is useless as its not talking anything abt speed when the trains meet. You never know what speed might be till that time.
Please note: Speed of Q is not constant throughout and its NOT possible to calculate distance travelled by it every hour.
Answer should be A.

Puys we have had a lot of discussion over this question..

I also had a similar confusion over option B, but it was made clear.

Can we please have the OA for this question?

guy_with_guts · August 7, 2009, 7:14am

Hey pj02, Vikram's explanation for quadrilateral sum is perfect ...to satisfy the second condition of one angle being twice the other, no where has it been mentioned it is applicable to non right angles only..
so for 90-90-45-135 satisfies because 90 is twice of 45 and has nothing to do with 45 and 135

If 2 angles are 90 in a quadrilateral, it does not imply other 2 are 90 as well...
I am sure u will be able to do it , else, draw a C, 2 edges are rt angles and stretch the lower or upper arm and join the slant line. other 2 are not 90 degrees

Ans E

yes ,You are right.i ws making a silly mistake w/o thnkng much.

shubhendu · August 7, 2009, 7:15am

Why other two will be 90?

We know one is 2 times the other. So its 60 and 120 thats the ONLY possibilility.

Ans should be E

By A-Any two angles can be 90 degrees(not sufficient)
By B-ABC is twice of BCD
Now ABC can be 90 which makes BCD 45,CDA 90/135,DAB 90/135
the eq 90+x+2x+90=360 is ruled out
coz here 2x can be 90(2x cannot be 180 as it in that case the 3 angles will be 180,90,90,sum of these 3 is eq to 360 ,which is nt psbl)
So E
I missed smthng here???

inder.14 · August 7, 2009, 10:54am

Is the measure of one of the interior angles of quadrilateral ABCD equal to 60 degrees?

(1) Two of the interior angles of ABCD are right angles.
(2) The degree measure of angle ABC is twice the degree measure of angle BCD.
Ans: Edited :biggrin:

Lets Take Option 1.
it says two interior angles are 90.
case 1) two adjacent angles are 90 in this case the remaining two angles can not not be found with given data
case 2) if two opposite angles are 90.then other two angles have to be 90.
so it is not sufficient.

Option 2 )
by second stament we can not be sure ..in this case one angle can be or can not be 60..

but by combining the two statment we can be sure the non of the interior angle can be 60.
so we can answer using both the statement.

please correct me if i am not..

regards,
Inder

pj02 · August 7, 2009, 1:21pm

NO dear , i am saying why choice A alone is not suffecient.When we know two angles are 90 , arn't the other two will be 90?
I tried to make a quadrilateral with two angles as 90 and other two different but................

hahaha

You want to say if two angles are 90 ,other two must be 90??

Thats not true dear...

You can draw it ..Try...

pj02 · August 7, 2009, 1:27pm

Hey pj02, Vikram's explanation for quadrilateral sum is perfect ...to satisfy the second condition of one angle being twice the other, no where has it been mentioned it is applicable to non right angles only..
so for 90-90-45-135 satisfies because 90 is twice of 45 and has nothing to do with 45 and 135

If 2 angles are 90 in a quadrilateral, it does not imply other 2 are 90 as well...
I am sure u will be able to do it , else, draw a C, 2 edges are rt angles and stretch the lower or upper arm and join the slant line. other 2 are not 90 degrees

Ans E

Yeppp.. i missed 45 *2 =90 wala case... Vikram... Good thinking..

Thanks for this explanation.

siddharthaduggirala · August 7, 2009, 7:47pm

puys i got the new 12 edition. i will do the qs over the week end and will try to post tough ques in DS and SC.

Sid

amsey1382 · August 7, 2009, 8:06pm

puys i got the new 12 edition. i will do the qs over the week end and will try to post tough ques in DS and SC.

Sid

OG -12???

even i'm up for this next week.........

CHeers

ponds_ggn · August 7, 2009, 10:52pm

puys i got the new 12 edition. i will do the qs over the week end and will try to post tough ques in DS and SC.

Sid

Always welcome Sid !