sameeruce08 wrote:
B Distance is 3 times longer than A
Doesn't it mean total distance is 4 times
Bunuel wrote:
From Aqua-Bella island, it is possible to reach Aqua-Marine island by either ferry A or ferry B. Ferry A sails 3 hours at 7 kilometers per hour, while ferry B takes a route that is three times longer. If ferry A is slower than ferry B by 2 kilometers per hour, how many hours longer is the journey of ferry B compared with the journey of ferry A ?
A. 4
B. 7
C. 8.6
D. 9.6
E. 12.6
Source:
Economist GMAT
The source is my insertion (per the question's tag).
In other words, however good this question may be, it is not an official question.
sameeruce08 , good catch. You wrote
B's distance is 3 times longer than A's
Doesn't it mean that B's total distance is 4 times that of A's distance?
The phrases "3 times longer than" and "3 times as long as" are hotly debated.*
In this case and similar others, translate "times longer than" with the emphases on
times -- on multiplication.
Treat "3 times longer than" as a multiplicative comparison, not as an additive or linear comparison.
B's distance = 3 * A's distanceWhy?1) STANDARD PARLANCEAs
KarishmaB notes , native English speakers in standard conversation use "3 times longer than" and "3 times as long as" interchangeably.
The two phrases mean the same thing: whatever A is, multiply it by 3.
Here: (my emphasis)
Quote:
Strictly mathematically, three times more would mean 4x but in regular parlance, 3 times older means 3x. So usually, in questions, when people come across 'three time more', they write it as 3x. Hopefully, GMAT will word the questions in a way to avoid this contradiction.
2) STANDARD PARLANCE and INTENDED TRANSLATIONBunuel concurs
here: (my emphasis)
Quote:
Question from GMAT Club member: BUT how can I properly express "1.5 times slower than normal" algebraically???
Bunuel: The wording of the question is not perfect (to say the least).
"Bill drove 1.5 times slower than normal"
is intended to be translated algebraically as t(today)=1.5*t(normal), where t stands for time.
If B were (4 * A), then B's distance would be (4 * 21) = 84 kilometers
B's rate is 9 km/hr. B's time would be 84/9 = 12 hours
A's time is 3 hours.
Time difference between A and B would be (12 - 3) = 9 hours
No answer is "9 hours"
In other words, interpret "B is 3 times longer than A" as
B is (3 * A)
B = 3A or
B is longer than A by a factor of 3
Maybe one example will make "standard parlance" more understandable:
5 days is 5
times longer than one day.
In one day there are 24 hours. In five days there are 120 hours. 120 = (5 * 24)
The word "times" refers to multiplication.
At the same time, 5 days is also 5
times as long as one day.
I do not recall having seen an official question that presents this issue, but my recall certainly is not definitive.
Hope that information helps.
*The discussion of X is 3 times longer than Y and X is 3 times as long as Y typically follows this course:
• Interpretation #1: longer by a FACTOR
If X is 3 times longer than Y, then X is longer than Y by a factor of 3. The comparison is multiplicative
Y = 10 miles
X = (10 * [factor of] 3) = 30 miles
• Interpretation #2: longer by a DIFFERENCE
If X is 3 times longer than Y, then X is longer than Y by a difference of 3 times the length of Y. The comparison is additive.
Y = 10 miles
X = 10 + (30) = 40 miles
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70% (01:23) correct 
