The figure above shows a construction plan for the intersect

Question

Roads.png The figure above shows a construction plan for the intersection of three straight roads, each having parallel edges and each having the same width. what is the value of t? (1) r = 140 (2) s = 160

Bunuel · Accepted Answer

https://gmatclub.com/forum/download/file.php?id=19252 The figure above shows a construction plan for the intersection of three straight roads, each having parallel edges and each having the same width. what is the value of t? (1) r = 140. Not sufficient. (2) s = 160. Not sufficient. (1)+(2) Consider the width of the roads to be 0 as shown below: Roads.png From the figure we have that r+s+t=360 degrees --> 140+160+t=360 --> t=60 degrees. Sufficient. Answer: C.

fozzzy · Answer

My net was lagging and wouldn't let me upload the image.

fozzzy · Answer

Seems a very basic question, but what other possible concepts are tested here? The official explanations was pretty convoluted had a parallelogram and all of that.

mydreammba · Answer

Bunnel

I have small doubt here

Suppose the length is not 0 then you will have two variables and you cannot solve the equation i.e the equation becomes

Suppose width=X

Then T= 360-3X-R-S

and here you have 2 variables and 1 equation you cannot get a single solution

Am i right?

Bunuel · Answer

No you are not. The edges of the road are parallel, so there is 0 degree angle between them.

mydreammba · Answer

Thanks Bunnel Got it

anshunadir · Answer

Bunuel - can you please elaborate it further ? why do we need to make this assumption ?

Regards.

Narenn · Answer

Go thru the file attached. Then you will understand the point which Bunuel is making.

Regards,

Abhijit

piyusharma · Answer

Hi Guys,

I assumed Angle R = Angle S due to the parallel lines property. Hence for me each statement was sufficient. Why is R not equal to S?

Ashishmathew01081987 · Answer

Because the two parallel lines you considered are not cut by the same traversal. So angle R is not equal to angle S.

KarishmaB · Answer

Also note that in DS questions, the two statements never contradict each other. If you had assumed that angle R = angle S, the two statements should have told you that that is not true. 
Statement 1 tells you that angle R is 140. According to you, then angle S should be 140 too. But statement 2 tells you that angle S is 160. This means there is something wrong in your assumption.

MathRevolution · Answer

Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

Attachment:

Roads.png [ 25.68 KiB | Viewed 15398 times ]

The figure above shows a construction plan for the intersection of three straight roads, each having parallel edges and each having the same width. what is the value of t?

(1) r = 140
(2) s = 160

From the original condition, we can see that there are 3 variables (r,s,t), and one equation (r+s+t=360), so we need 2 more equations, which are given from the 2 conditions, so there is high chance (C) will be our answer.
Looking at the conditions together, r+s+t=140+160+t=360, so it answers the question 'yes', and the answer becomes (C).

For cases where we need 2 more equation, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.

Avinash_R1 · Answer

Can you please explain how to answer this question?

gmexamtaker1 · Answer

https://gmatclub.com/forum/download/file.php?id=19252 The figure above shows a construction plan for the intersection of three straight roads, each having parallel edges and each having the same width. what is the value of t? (1) r = 140. Not sufficient. (2) s = 160. Not sufficient. (1)+(2) Consider the width of the roads to be 0 as shown below: Roads.png From the figure we have that r+s+t=360 degrees --> 140+160+t=360 --> t=60 degrees. Sufficient. I cannot understand the thinking process that results in witdth=0 can someone elaborate?

bumpbot · Answer

Automated notice from GMAT Club BumpBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

The figure above shows a construction plan for the intersect

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Data Sufficiency (DS) Questions

The figure above shows a construction plan for the intersect

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards