Silly Mistakes

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wmg

208 posts

wmg

#1 h Mar 15, 2013, 8:17 PM • 2 Y

Y by Adventure10, Mango247

So I scored way lower than I should have on the AIME I. I probably got a 5~6.

I made some seriously dumb mistakes. I had the ingenious idea of counting all the possible ways in #2, (where the problem simplified to b+c+d = mult. 5) and miscounted because I forgot one case. The worst thing is I checked my counting 2-3 times and came up with the same answer. I also missed #6 because I did 3!*9!*3/12! instead of (3!*9! + 4!*9! + 5!*9!)/12!. I'm getting seriously demoralized, as next year is my last year that I'm eligible for JMO qualification (I also forgot to multiply by 3 on an AMC10 Question). My JMO index should've been a 207.5, but it's going to be like 181.5 now :/

How does one avoid things like this? It seems that I'm messing up most on counting questions.

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ZackMan

57 posts

ZackMan

#2 h Mar 15, 2013, 9:45 PM • 2 Y

Y by Adventure10, Mango247

For #2, you can pick any b and c and there would be 2 choices for d so 10*10*2=200
As for avoid mistakes in general, just try to simplify the problem and don't be messy.
I feel your pain because I got a 9 on the aime but only 94 on amc 12 lol (2 dumb mistakes plus hard test)... I only started practicing for real after I bombed the amcs.
No way 184 can qualify unless I'm super lucky.

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v_Enhance

6870 posts

v_Enhance

#3 h Mar 15, 2013, 10:06 PM • 73 Y

Y by sindennisz, Tuxianeer, happysmileyface, baijiangchen, El_Ectric, turkeybob777, ssilwa, dft, negativebplusorminus, iwantcombo, mathway, AwesomeToad, brandbest1, Royalreter1, flamefoxx99, carelessmistakes, sicilianfan, TheMaskedMagician, droid347, cnnwy1282, fz0718, spartan168, WolfOfAtlantis, MSTang, ahaanomegas, C-bass, in8, AMN300, dantx5, rjiang16, pandyhu2001, afroromanian, Mathaddict11, mathmaster2000, amplreneo, librian2000, DivideBy0, spin8, mrowhed, bestwillcui1, ImpossibleCube, sophie8, budu, mathathlete06, KenV, cakeguy, Iamawesome1, RamanConjecture, yousseframzi, Vndom, anonman, Zorger74, Williamgolly, HamstPan38825, vsamc, IceWolf10, Adventure10, Mango247, and 15 other users

We're not kidding when we say to be neat. Since I'm feeling generous, I've attached a copy of my scratch paper from this year's AIME (or at least some nontrivial subset of it) to give you an idea of what kind of organization I use.

Also, don't misread questions, don't rush, etc.

Anyways there's not always a whole lot you can do about it. This was the first year where I was able to look at a problem and basically know how to do it within one or two minutes; this left me a lot of time for computation, and consequently I made very few errors as compared to previous years. In other words, as you get better at problem-solving you'll naturally become less likely to make careless errors as well. (At least that's how it turned out for me.)

Attachments:

AIME.pdf (4308kb)

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ZackMan

57 posts

ZackMan

#4 h Mar 15, 2013, 11:19 PM • 2 Y

Y by Adventure10, Mango247

Wow, I really wished I spent more time on #5, so easy! This is really disappointing because I am a sophomore and this is my first year practicing. Wish I started earlier.

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v_Enhance

6870 posts

v_Enhance

#5 h Mar 18, 2013, 2:34 AM • 4 Y

Y by ssk9208, HamstPan38825, Adventure10, and 1 other user

Going off what I said earlier, here's a good example of something you do *not* want in your scratch paper: $\frac{\frac{32}{25}}{4} = \frac{8}{25} \cdot 5 = \frac{8}{5} \cdot 2 = \frac{16}{5} = 21 \quad \boxed{B}$ (cf. AMC 12B 2013, Problem 19)

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mathwizard888

1635 posts

mathwizard888

#6 h Mar 18, 2013, 9:32 PM • 2 Y

Y by Adventure10, Mango247

I choked more on this test than anything else...

#2:Decided to count all the ways by hand and messed up

#7:Found half the height, then forgot to double it

#8:Thought 3*2013=2013

#9:Apparently I can't simplify expressions with square roots

So now my JMO index is a borderline 213.5, as opposed to a 253.5, which would easily qualify.

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torquoiseworld

163 posts

torquoiseworld

#7 h Mar 19, 2013, 12:48 AM • 1 Y

Y by Adventure10

v_Enhance wrote:

We're not kidding when we say to be neat. Since I'm feeling generous, I've attached a copy of my scratch paper from this year's AIME (or at least some nontrivial subset of it) to give you an idea of what kind of organization I use.

Also, don't misread questions, don't rush, etc.

Anyways there's not always a whole lot you can do about it. This was the first year where I was able to look at a problem and basically know how to do it within one or two minutes; this left me a lot of time for computation, and consequently I made very few errors as compared to previous years. In other words, as you get better at problem-solving you'll naturally become less likely to make careless errors as well. (At least that's how it turned out for me.)

what do you mean by risk on the scratch sheets?

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forthegreatergood

2739 posts

forthegreatergood

#8 h Mar 19, 2013, 1:06 AM • 1 Y

Y by Adventure10

Yeah what do you mean? It looks very neat by the way

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v_Enhance

6870 posts

v_Enhance

#9 h Mar 19, 2013, 1:41 AM • 3 Y

Y by HamstPan38825, Adventure10, Mango247

Oh, that was just something I made up during the test this year. Right after I solved each problem I would estimate how likely it was that I screwed up by putting a number there -- scale runs from 0 to 7.

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TMTOLBTWNTOF

18 posts

TMTOLBTWNTOF

#10 h Mar 19, 2013, 3:15 AM • 2 Y

Y by Adventure10, Mango247

The AIME leaves you with a lot more time than the AMC, so you have a lot of time to look over your answers and think about each problem.

I would recommend SHOWING ALL YOUR WORK.

Even though it's not necessary to get an answer, it makes checking your answers a lot easier, and you can easily spot what went wrong.

For the AMC, however, the only thing I can really say is for you to read the problems thoroughly and have mighty concentration, because you don't have the time you do on the AIME.

Also brute force is a bad idea.

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mentalgenius

1020 posts

mentalgenius

#11 h Mar 19, 2013, 3:25 AM • 3 Y

Y by DivideBy0, Adventure10, Mango247

Also, don't use all those wacky "speed tricks" for your computations; you can use them your second or third time around to check every step, but don't rely solely on them -- making a stupid computational error really sucks.

So if I am presented with something like 59 * 7 on an AIME, and I have > 2 minutes left, I do the following:

(50*7 + 9*7)
(60*7 - 1*7)
actually write out 59 * 7 and do it

Doing every calculation > 2 times really helps improve your accuracy. And most of the time, when I do it 3 ways, I did one of them wrong and catch my silly computation mistake. Trust me, this does wonders.

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dinoboy

2903 posts

dinoboy

#12 h Mar 19, 2013, 3:26 AM • 2 Y

Y by Adventure10 and 1 other user

Hmm actually using speed tricks is the right way to go for your first time around, as they help you get onto later problems sooner. However, you should always do the "slower way" while checking.

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mentalgenius

1020 posts

mentalgenius

#13 h Mar 19, 2013, 3:35 AM • 1 Y

Y by Adventure10

I guess you can switch the order around a little bit like that, but my main point was not to rely solely upon them.

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