Metro City street cleaning occurs according to the following schedule:

Question

• First Street: every Thursday

• Second Street: every fourth Tuesday

• Third Street: every Monday

• Central Street: every third Wednesday

• Grand Street: every fourth Saturday

• Main Street: every second Friday

Select for  X  and for  Y  two streets such that every cleaning of the street chosen for  X  must be followed on the next day by a cleaning of the street chosen for  Y , consistent with the given information. Make only two selections, one in each column.

https://gmatclub.com/forum/download/file_private.php?id=76188

anish777 · Answer

Hi  chetan2u 
Consider the situation, every second friday main street cleaning happens which is followed by the cleaning in first street in thursday. Hence, X can be main street and Y can be first street.
What is wrong here ?
Thanks
Anish

chetan2u · Answer

Hi Anish

Every cleaning on a given day in X should be followed by cleaning on next day on Y.
If you take X as the main street. X gets cleaned every second Friday, so Y should get cleaned at least on every second Saturday. But first street gets cleaned on every Thursday.

Thus, in your example, Y happens first and X happens on the next day. Actually, it has to be the other way.

DrAnkita91 · Answer

how did we come to this?? whats the logic? please can you explain
"This means we take a street which is less often cleaned as X and more frequently cleaned as Y"

Juliana98 · Answer

the question wants a day (x) where we will have a consequent day (y) that will be cleaned. so if X is cleaned, then Y is cleaned the day after. I tried using options for X an pair them with Y. For example: if X is is  • First Street: every Thursday, then we need a Y that is cleaned every Friday, and there is no such street cleaned every Friday, so X could not be First Street, then X: Second Street: every fourth Tuesday, then we will need a Y that is cleaned every Wednesday, and there is no such Y for example if x is Second Street and Y is Central Street: every third Wednesday, they could coincide or not, so X could not be Second street.But if X is Central Street: every third Wednesday, we will have a Y that will ALWAYS be cleaned after X, y will be First Street: every Thursday. we don not. care if X is all Wednesdays cleaned, we only care that if X is cleaned, as it says even 3 Wednesdays, we for sure will have the next day Y First Street: every Thursday cleaned. for example

monday: 
 Tuesday 
 Wednesday: X Central Street: every third Wednesday 
 Thursday: Y First Street: every Thursday 
 friday 
 Saturday

monday:
Tuesday
Wednesday: here there will no be cleaning since it is every 3 Wednesday 
 Thursday: Y First Street: every Thursday
friday
Saturday

monday:
Tuesday
Wednesday: here there will no be cleaning since it is every 3 Wednesday
Thursday: Y First Street: every Thursday
friday
Saturday

NOW THE SEQUENCE REPETS AGAIN

monday: 
 Tuesday 
 Wednesday: X Central Street: every third Wednesday 
 Thursday: Y First Street: every Thursday 
 friday 
 Saturday

chetan2u · Answer

A quick way would be logical way to tackle it but the solution in the video would surely be a safer way to get to the answer.

Logical way: every cleaning of the street chosen for X must be followed on the next day by a cleaning of the street chosen for Y,

This means we take a street which is less often cleaned as X and more frequently cleaned as Y.

So Y should be checked for the ones cleaned every week. Every Monday and every Thursday.
Look for X as some street that is cleaned on a day prior that is Sunday or Wednesday. We have Central street being cleaned every third Wednesday.

Thus the two options that fit in are
X: Central street - every third Wednesday
Y: First street - every Thursday

https://www.youtube.com/watch?v=mBedPGbF3Vk

MyNameisFritz · Answer

Even though I got this question wrong in the mock, it's actually quite simple.

The question basically asks: "Which street will ALWAYS be cleaned the next day if you choose street X first?"

There is only 1 solution: every time you choose Central street, always the next day First street has to be cleaned.

Dream009 · Answer

This took me 2 mins but this is how I solved. We need pairs ok
Mon Tues
Tues, wed
wed, thurs
thurs, frid
Frid, Satu

Now it cannot happen that a cleaning happens say on first day and not on second day....let's start elimination

Mon Tues - every monday will not have tues cleaning - out
Tues, wed - Can be a tuesday without wed cleaning - out
wed, thurs - yes every wed cleaning (even if it happens in 3rd week) will have thurs
thurs, frid - No
Frid, Satu - Nopes - don't get confused here - there can be a friday without Saturday cleaning.

This still took 2 mins

AndyRugger · Answer

This question is definitely easier to answer with a table. I made a table showing column headings:

M-Tu-W-Th-Fr-S

With rows for:

- Street Name
- Street Frequency

And the answer jumps out at you pretty quickly in that format.

Metro City street cleaning occurs according to the following schedule:

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X	Y
		First Street
		Second Street
		Third Street
		Central Street
		Grand Street
		Main Street

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Metro City street cleaning occurs according to the following schedule:

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