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Re: Lee is planning a trip and estimates that, rounded to the nearest 5 [#permalink]
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Iwillget770 wrote:
Lee is planning a trip and estimates that, rounded to the nearest 5 kilometers (km), the length of the trip will be 560 km and that, rounded to the nearest ​​ hour, the driving time for the trip will be 7 hours. If these estimates are correct, then Lee’s average driving speed during the trip will be between __x__ kilometers per hour and _y__ kilometers per hour, where x < y.

From the values given in the table, select for x and for y the values that complete the statement in such a way that the interval between the selected values includes all possible average speeds for Lee's trip and y – x is minimal. Make only two selections, one in each column.

­
Hi,

Is this question from GMAT Prep Focus? Thank you!
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Re: Lee is planning a trip and estimates that, rounded to the nearest 5 [#permalink]
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Bunuel wrote:
Iwillget770 wrote:
Lee is planning a trip and estimates that, rounded to the nearest 5 kilometers (km), the length of the trip will be 560 km and that, rounded to the nearest ​​ hour, the driving time for the trip will be 7 hours. If these estimates are correct, then Lee’s average driving speed during the trip will be between __x__ kilometers per hour and _y__ kilometers per hour, where x < y.

From the values given in the table, select for x and for y the values that complete the statement in such a way that the interval between the selected values includes all possible average speeds for Lee's trip and y – x is minimal. Make only two selections, one in each column.

­
Hi,

Is this question from GMAT Prep Focus? Thank you!

­Hi Bunuel,

No, it is from online question bank of Official Guide Data Insights 2023-24­
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Re: Lee is planning a trip and estimates that, rounded to the nearest 5 [#permalink]
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Iwillget770 wrote:
Bunuel wrote:
Iwillget770 wrote:
Lee is planning a trip and estimates that, rounded to the nearest 5 kilometers (km), the length of the trip will be 560 km and that, rounded to the nearest ​​ hour, the driving time for the trip will be 7 hours. If these estimates are correct, then Lee’s average driving speed during the trip will be between __x__ kilometers per hour and _y__ kilometers per hour, where x < y.

From the values given in the table, select for x and for y the values that complete the statement in such a way that the interval between the selected values includes all possible average speeds for Lee's trip and y – x is minimal. Make only two selections, one in each column.

­
Hi,

Is this question from GMAT Prep Focus? Thank you!

­Hi Bunuel,

No, it is from online question bank of Official Guide Data Insights 2023-24­

­
Thank you very much.
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Re: Lee is planning a trip and estimates that, rounded to the nearest 5 [#permalink]
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Please post the questions clearly and exactly the way they are given. You have written option E as 83, while it is 85.<br />
Although it did not make a difference here but could have easily affected the answer in some other case.­
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Re: Lee is planning a trip and estimates that, rounded to the nearest 5 [#permalink]
 
chetan2u wrote:
Say distance is between 5 to 10: ­Nearest 5 km means the distance is rounded off to 5, if the distance is <7.5, otherwise rounded off to 10.
Thus, in case of 560, the distance would lie in range => \(557.5 \leq D < 562.5\)

Similarly, the hours would be in range ­=>  \((6-\frac{1}{2}*\frac{1}{4}) \leq D < (6+\frac{1}{2}*\frac{1}{4})\) = \(6.875 \leq D < 7.125\)

Minimum average speed = smallest distance in maximum time = \(\frac{557.5}{7.125}=78.25\)
Maximum average speed = largest distance in minimum time = \(\frac{562.5}{6.875}=81.81\)
±
Thus, the range should contain all values from 78.25 to 81.81

Since y-x has to be minimal, look for an option just below 78.25 for x, and look for an option just above 81.81 for y.
x = 76 and y=82

 

­Hi chetan2u,

I didn't understand the rounding off part. While solving I did 560 ± 5 and arrived at 565 and 555 respectively and similarly for time 7 ± 0.25 and arrived at 6.75 and 7.25. Applied the logic of inverse relation for distance and time got the results as 83.7 and 76.55.

Is this correct approach ?
 ­
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Re: Lee is planning a trip and estimates that, rounded to the nearest 5 [#permalink]
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jack5397 wrote:
chetan2u wrote:
Say distance is between 5 to 10: ­Nearest 5 km means the distance is rounded off to 5, if the distance is <7.5, otherwise rounded off to 10.
Thus, in case of 560, the distance would lie in range => \(557.5 \leq D < 562.5\)

Similarly, the hours would be in range ­=>  \((6-\frac{1}{2}*\frac{1}{4}) \leq D < (6+\frac{1}{2}*\frac{1}{4})\) = \(6.875 \leq D < 7.125\)

Minimum average speed = smallest distance in maximum time = \(\frac{557.5}{7.125}=78.25\)
Maximum average speed = largest distance in minimum time = \(\frac{562.5}{6.875}=81.81\)
±
Thus, the range should contain all values from 78.25 to 81.81

Since y-x has to be minimal, look for an option just below 78.25 for x, and look for an option just above 81.81 for y.
x = 76 and y=82


 

­Hi chetan2u,

I didn't understand the rounding off part. While solving I did 560 ± 5 and arrived at 565 and 555 respectively and similarly for time 7 ± 0.25 and arrived at 6.75 and 7.25. Applied the logic of inverse relation for distance and time got the results as 83.7 and 76.55.

Is this correct approach ?
 ­

­No, that will not be correct.

What you are doing is rounding off to nearest 10. But here it is rounding off to nearest 5. This means the number will be rounded off to 555 or 560. If it is < (555+560)/2 or <557.5, then it is rounded off to 555, otherwise to 560.

Hope it resolves your doubt.
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Re: Lee is planning a trip and estimates that, rounded to the nearest 5 [#permalink]
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Iwillget770 wrote:
­
All Data Insight question: TPA [ Official Guide DI Review 2023-24] 



Lee is planning a trip and estimates that, rounded to the nearest 5 kilometers (km), the length of the trip will be 560 km and that, rounded to the nearest ​​ hour, the driving time for the trip will be 7 hours. If these estimates are correct, then Lee’s average driving speed during the trip will be between __x__ kilometers per hour and _y__ kilometers per hour, where x < y.

From the values given in the table, select for x and for y the values that complete the statement in such a way that the interval between the selected values includes all possible average speeds for Lee's trip and y – x is minimal. Make only two selections, one in each column.­
 

rounded to the nearest 5 kilometers (km), the length of the trip will be 560 km. So rounded to 550, 555, 560, 565 etc. Length of trip will be 

557.5 <= L < 562.5 
If it is less than 557.5, say 556, it will get rounded off to 555. If it is say 563, it will get rounded off to 565. 

rounded to the nearest ​​ hour, the driving time for the trip will be 7 hours. So rounded to 6.5 hrs, 6.75 hrs, 7 hrs, 7.25 hrs etc. Time taken will be 

6.875 <= T < 7.125 
If it is less, say 6.8 hrs, it will get rounded to 6.75 etc. 

For lowest speed, distance will be minimum and time taken will be maximum possible = 557.5/7.125 = 78.2
For maximum speed, distance will be maximum and time taken will be minimum possible = 562.5/6.875 = 81.8

Now the tricky part is the options to choose. Given: 
"... the interval between the selected values includes all possible average speeds for Lee's trip and y – x is minimal."

So the interval should include ALL possible values of speeds and it should be the smallest possible (of the given options). So 76 - 82 includes all possible values in the smallest range. For example, 73 - 82 also includes all possible values but its not the smallest range. 
Hence select 76 and 82. ANSWER








­
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