A low-pressure weather system

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juliette: Newbie | Next Rank: 10 Posts; Posts: 5; Joined: Mon Mar 08, 2010 6:09 am

by juliette » Fri Mar 19, 2010 10:22 pm

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 determine 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 near by towns

I'm confused between B and C
It tells us that rainfall results from about 70% of a low-pressure weather system, which gives us the relationship between rainfall and low-pressure weather system. I think both B and C can determine the probability of having a thundershower, as rainfalls and the low-pressure weather system have a correlation.

Source: Beat The GMAT — Critical Reasoning | Fri Mar 19, 2010 10:22 pm

kstv: Legendary Member; Posts: 610; Joined: Fri Jan 15, 2010 12:33 amFollowed by: 2 members; Thanked: 47 times

by kstv » Fri Mar 19, 2010 10:42 pm

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 determine the probability that Plainville will have a thundershower soon?

70 % of such Low pressure system in Plainville result in rainfall.
Thunder storms from such system are very likley in spring . (C) will give us this % but for not specifically for spring. Whereas B will us spring rainfall that are thunder storms.

We know there is a 70% chance of rainfall. Ot this 70% if we know the percentage that are thunderstorms, which (B) promises to reveal we will know the probability of thunderstorm. Suppose (B) says there is a 40% of spring rainfall are thunderstorms. We can say there is a 28% chance of thunderstorms.
If (C) tells us there is a 40% chance of thunderstorm from low pressure is more exact than the Premise - Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems
IMO B

juliette: Newbie | Next Rank: 10 Posts; Posts: 5; Joined: Mon Mar 08, 2010 6:09 am

by juliette » Fri Mar 19, 2010 10:47 pm

kstv wrote: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 determine the probability that Plainville will have a thundershower soon?

70 % of such Low pressure system in Plainville result in rainfall.
Thunder storms from such system are very likley in spring . (C) will give us this % but for not specifically for spring. Whereas B will us spring rainfall that are thunder storms.

We know there is a 70% chance of rainfall. Ot this 70% if we know the percentage that are thunderstorms, which (B) promises to reveal we will know the probability of thunderstorm. Suppose (B) says there is a 40% of spring rainfall are thunderstorms. We can say there is a 28% chance of thunderstorms.
If (C) tells us there is a 40% chance of thunderstorm from low pressure is more exact than the Premise - Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems
IMO B

I think I get it~thank you so much

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