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rainfall problem

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kiennguyen: Senior | Next Rank: 100 Posts; Posts: 73; Joined: Sat Oct 03, 2009 10:37 pm

by kiennguyen » Thu Nov 05, 2009 7:19 pm

imo D. OA pls

Testluv: GMAT Instructor; Posts: 1302; Joined: Mon Oct 19, 2009 2:13 pmFollowed by: 164 members; Location: Toronto; Thanked: 539 times; GMAT Score:800

by Testluv » Thu Nov 05, 2009 7:47 pm

kiennguyen wrote:imo D. OA pls

Hi kiennguyen,

Actually, choice D is mathematically impossible. This is because the range for moderate rain is something just over 1 inch up to 2 inches.

To test it, let's maximize rain per moderately rain in 1990 at 2 inches, and minimize rain per moderately rainy day in 1910 at 1.00000.....1 inch.

So if you had an equal number of moderately rainy days in both years, then the ratio of 1990 mod rain/1910 mod rain would be: 2/1.0000.....1. This already makes it mathematically impossible.

But of course, there were fewer moderately rainy days in 1990, which means there were more in 1910, so our ratio would really look like: 2/(1.00000...1+).

Which means it is mathematically impossible for the amount of rain that fell on moderately rainy days in 1990 to have been more than twice as great as the amount of rain that fell on moderately rainy days in 1910.

Last edited by Testluv on Thu Nov 05, 2009 11:47 pm, edited 1 time in total.

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kiennguyen: Senior | Next Rank: 100 Posts; Posts: 73; Joined: Sat Oct 03, 2009 10:37 pm

WOW!

by kiennguyen » Thu Nov 05, 2009 11:26 pm

Testluv wrote:
kiennguyen wrote:imo D. OA pls
Hi kiennguyen,

Actually, choice D is mathematically impossible. This is because the range for moderate rain is something just over 1 cm up to 2 cm.

To test it, let's maximize rain per moderately rain in 1990 at 2 inches, and minimize rain per moderately rainy day in 1910 at 1.00000.....1 inch.

So if you had an equal number of moderately rainy days in both years, then the ratio of 1990 mod rain/1910 mod rain would be: 2/1.0000.....1. This already makes it mathematically impossible.

But of course, there were fewer moderately rainy days in 1990, which means there were more in 1910, so our ratio would really look like: 2/(1.00000...1+).

Which means it is mathematically impossible for the amount of rain that fell on moderately rainy days in 1990 to have been more than twice as great as the amount of rain that fell on moderately rainy days in 1910.

thanks, Testluv! i didn't see your post before i gave my idea! your explanation is perfect. i hope you can help me out in the future!

mehravikas: Legendary Member; Posts: 1161; Joined: Mon May 12, 2008 2:52 amFollowed by: 1 member; Location: Sydney; Thanked: 23 times

by mehravikas » Thu Nov 12, 2009 12:15 pm

IMO - D

gettingready: Newbie | Next Rank: 10 Posts; Posts: 5; Joined: Mon Nov 09, 2009 10:27 am

by gettingready » Fri Nov 13, 2009 2:18 pm

Hello crackgmat007,

Thank you for your very detailed explanation. I was going for D. Although, I perfectly understood your explanation of why D is not correct, to me choice A still does not make sense.Could you possible deepen the explanation of why A is correct? Or is it more of " the best choice" out of the worst?
Thanks

palvarez: Master | Next Rank: 500 Posts; Posts: 199; Joined: Sat Oct 24, 2009 4:43 pm; Thanked: 22 times; GMAT Score:710

by palvarez » Fri Nov 13, 2009 3:35 pm

gettingready wrote:Hello crackgmat007,

Thank you for your very detailed explanation. I was going for D. Although, I perfectly understood your explanation of why D is not correct, to me choice A still does not make sense.Could you possible deepen the explanation of why A is correct? Or is it more of " the best choice" out of the worst?
Thanks

I know why it doesn't take sense for (A) to be correct. But notice the modal quantifier "possibly". Possibly true is not same as necessarily true. (A) is not necessarily true, but possibly true.

When it comes to D, it is not possibly true, which means "necessarily" false.

Not (possibly true) = (not possibly) (not true) = necessarily false.

heshamelaziry: Legendary Member; Posts: 869; Joined: Wed Aug 26, 2009 3:49 pmFollowed by: 3 members; Location: California; Thanked: 13 times

by heshamelaziry » Fri Nov 13, 2009 4:32 pm

Testluv wrote:
kiennguyen wrote:imo D. OA pls
Hi kiennguyen,

Actually, choice D is mathematically impossible. This is because the range for moderate rain is something just over 1 inch up to 2 inches.

To test it, let's maximize rain per moderately rain in 1990 at 2 inches, and minimize rain per moderately rainy day in 1910 at 1.00000.....1 inch.

So if you had an equal number of moderately rainy days in both years, then the ratio of 1990 mod rain/1910 mod rain would be: 2/1.0000.....1. This already makes it mathematically impossible.

But of course, there were fewer moderately rainy days in 1990, which means there were more in 1910, so our ratio would really look like: 2/(1.00000...1+).

Which means it is mathematically impossible for the amount of rain that fell on moderately rainy days in 1990 to have been more than twice as great as the amount of rain that fell on moderately rainy days in 1910.[/quot

Testluv, is this a LSAT type question ?

Thanks,

Testluv: GMAT Instructor; Posts: 1302; Joined: Mon Oct 19, 2009 2:13 pmFollowed by: 164 members; Location: Toronto; Thanked: 539 times; GMAT Score:800

by Testluv » Fri Nov 13, 2009 5:11 pm

Testluv, is this a LSAT type question ?

Nope. This is a high-level GMAT kind of question. LSAT won't test quant this furiously.

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dare2dream: Junior | Next Rank: 30 Posts; Posts: 20; Joined: Fri Sep 25, 2009 2:26 am; Thanked: 1 times

by dare2dream » Sat Nov 14, 2009 8:19 am

I will choose C between A & C. D is absolutely ruled out.

getso: Master | Next Rank: 500 Posts; Posts: 141; Joined: Sat Feb 28, 2009 8:19 am; Thanked: 1 times

by getso » Sat Nov 14, 2009 9:59 am

Hi Testluv,

Great explanation

Could you please give us more tips and tricks such questions. It would be very helpful.

james33: Master | Next Rank: 500 Posts; Posts: 200; Joined: Sat Aug 22, 2015 10:27 am

by james33 » Sun May 15, 2016 10:09 pm

I believe the correct answer should be D

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