GMAT Verbal: Critical Reasoning (CR)

PSUSHMA123 · #1 (**permalink**) July 23rd, 2008, 12:10 PM

21. A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area. Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in Plainville.
Knowing which one of the following, in addition to the information above, would be most useful for determining the probability that Plainville will have a thundershower soon?
(A) the percentage of thundershowers in Plainville that occur in the spring
(B) the percentage of spring rainfalls in Plainville that are thundershowers
(C) the percentage of thundershowers in Plainville that result from low-pressure systems
(D) whether low-pressure systems in other areas are associated with rainfall
(E) whether Plainville has more or fewer thundershowers each spring than do nearby towns

how to answer this question

raveena · #2 (**permalink**) July 23rd, 2008, 12:27 PM

IMO C.

If we know that how much percentage of thundershowers result from low presure systems ..if the percentage is more then the chances that the plainvill will get the thunderstorm soon will be strengthen since low pressure system is approaching

kidz · #3 (**permalink**) July 23rd, 2008, 12:34 PM

B for me .... connects rainfall, low pressure systems and thunderstorms....

Whats the official answer ?

anilsoujanya · #4 (**permalink**) July 23rd, 2008, 03:40 PM

I agree with B. Its given that 70% chance that it will rain. We need the probability that it is going to be a thunderstorm.
The problem with 'C' is that it is not specific to spring. Since spring is the season that thunderstorms are more likely to occur, we get very conservative estimate...

tintinusa · #5 (**permalink**) July 23rd, 2008, 08:49 PM

Confused....Will select "A" in crisis. Might be wrong!!! Whats the OA

rose · #6 (**permalink**) July 24th, 2008, 01:47 AM

i will go with B

deepaky2222 · #7 (**permalink**) July 24th, 2008, 05:33 AM

ya b is the right answer....

onlyumesh · #8 (**permalink**) July 25th, 2008, 02:56 PM

in my opinion B is the answer..
A does not say anything about the lps and thundershower...where as from B we can relate these two..
for example..
the percentage of spring rainfalls in Plainville that are thundershowers is 30%
from the problm statement chance of lps in rainfall is 70%
so the chance of lpa for thunder shower=0.7*0.3=0.21..hence information provided in B is useful

T-Bag · #9 (**permalink**) July 28th, 2008, 06:40 AM

Is it B?