Is the number of seconds required to travel D feet at R feet per second greater than the number of seconds to travel T feet at F feet per second?
1. D is 30 greater than T
2. R is 30 greater than F
[spoiler]This is Q87 from OG12, OA is E, but I am convinced the answer is C. When both statements are combined the question becomes is (T+30)/(F+30) > T/F right? In that case the answer should be 'yes'. OG gives no explanation, so please enlighten me if you understand. Thanks[/spoiler]
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- wayofjungle
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1) D=30+T; since we don't have information about R and F hence 1 alone is not sufficient to answer the question.wayofjungle wrote:Is the number of seconds required to travel D feet at R feet per second greater than the number of seconds to travel T feet at F feet per second?
1. D is 30 greater than T
2. R is 30 greater than F
[spoiler]This is Q87 from OG12, OA is E, but I am convinced the answer is C. When both statements are combined the question becomes is (T+30)/(F+30) > T/F right? In that case the answer should be 'yes'. OG gives no explanation, so please enlighten me if you understand. Thanks[/spoiler]
2) R=30+F; since we don't have information about D and T hence 2 alone is not sufficient to answer the question.
combining 1 and 2 we have;
D=30+T and R=30+F;
therefore time taken in traveling D feet= 30+T/30+F;
and time taken in traveling T feet = T/F;
if T=F=2; we have time taken in traveling D and T feet=1 seconds;
if T=4 and F=2; time taken in traveling D distance would be; 34/32=17/16~1.06; while T/F=4/2=2;
as different results are possible depending upon different values of T and F hence answer should be E
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- smackmartine
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IMO E
R(S1) = D & T(S2) = F , where S1 and S2 are respective times(in sec)
Asked : S1-S2 is -ve or positive
1) D=T+30 , NO info about relation between Rates --> Insufficient
2) R=F+30 , NO info about relation between distance--> Insufficient
Combining 1 and 2
S1-S2 = (D/R) - (F/T) = (T+30)/R - (R-30)/T ----> There is no way we can solve this expression using two unknown variables , So Insufficient
R(S1) = D & T(S2) = F , where S1 and S2 are respective times(in sec)
Asked : S1-S2 is -ve or positive
1) D=T+30 , NO info about relation between Rates --> Insufficient
2) R=F+30 , NO info about relation between distance--> Insufficient
Combining 1 and 2
S1-S2 = (D/R) - (F/T) = (T+30)/R - (R-30)/T ----> There is no way we can solve this expression using two unknown variables , So Insufficient
- wayofjungle
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Yikes. I was stuck on the concept as discussed on page 28 of the 2nd MGMAT Guide (Fractions, Decimals...) which states:
"Adding the same number to BOTH the numerator and denominator brings the fraction CLOSER TO 1, regardless of the fraction's value"
In this problem I neglected to consider the case where T/F is not truly a fraction but instead simply a division operation of two variables where T > F, or a mixed number.
Thanks for helping me get smarter!
"Adding the same number to BOTH the numerator and denominator brings the fraction CLOSER TO 1, regardless of the fraction's value"
In this problem I neglected to consider the case where T/F is not truly a fraction but instead simply a division operation of two variables where T > F, or a mixed number.
Thanks for helping me get smarter!
- GMATGuruNY
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Question: Is D/R > T/F?wayofjungle wrote:Is the number of seconds required to travel D feet at R feet per second greater than the number of seconds to travel T feet at F feet per second?
1. D is 30 greater than T
2. R is 30 greater than F
[spoiler]This is Q87 from OG12, OA is E, but I am convinced the answer is C. When both statements are combined the question becomes is (T+30)/(F+30) > T/F right? In that case the answer should be 'yes'. OG gives no explanation, so please enlighten me if you understand. Thanks[/spoiler]
Since the question is restricted to positive integers, we can cross-multiply and rephrase the question:
Is DF > RT?
Statement 1: D is 30 greater than T.
No information about F or R.
Insufficient.
Statement 2: R is 30 greater than F.
No information about D or T.
Insufficient.
Statements 1 and 2 combined:
D is 30 greater than T and R is 30 greater than F.
Is DF > RT?
Let T=1, D=31, F=1, R=31.
Is 31*1 > 31*1? No.
Let T=1, D=31, F=2, R=32.
Is 31*2 > 32*1? Yes.
Since the answer can be both No and Yes, insufficient.
The correct answer is E.
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I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
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- bblast
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this tests a fundamental concept of ratios.
"if the same number is added to the numerator and denominator a fraction:
1> if the fraction is proper the value of fraction increases
example
1/3 - add 1 to both num and denominator- fraction increases to 2/4
2> if the fraction is improper the value of fraction decreases"
example
3/2 - add 1 to both num and denominator- fraction decreases to 4/3
Hence in this solution we cannot say which of the fractions is larger.
(T+30)/(F+30)
OR
T/F
Mitch, please Correct me if I am wrong
"if the same number is added to the numerator and denominator a fraction:
1> if the fraction is proper the value of fraction increases
example
1/3 - add 1 to both num and denominator- fraction increases to 2/4
2> if the fraction is improper the value of fraction decreases"
example
3/2 - add 1 to both num and denominator- fraction decreases to 4/3
Hence in this solution we cannot say which of the fractions is larger.
(T+30)/(F+30)
OR
T/F
Mitch, please Correct me if I am wrong
Cheers !!
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Quant 47-Striving for 50
Verbal 34-Striving for 40
My gmat journey :
https://www.beatthegmat.com/710-bblast-s ... 90735.html
My take on the GMAT RC :
https://www.beatthegmat.com/ways-to-bbla ... 90808.html
How to prepare before your MBA:
https://www.youtube.com/watch?v=upz46D7 ... TWBZF14TKW_