Mental math--sign of intelligence?

[funshine]

Kinda off-topic, but I was calculating housing costs today and was reminded of how much I suck at mental math. Here's my question:

When you multiply/add/divide in your head, do you have trouble holding all the numbers in your head? Because I do--it requires so much concentration on my part, and I'm soooo slow, not to mention frequently inaccurate because I forget the numbers I was initially multiplying/dividing. I've wondered if it's something that gets better the more you do it, or if some people (like me!) just don't have enough working memory to do mental math quickly!

Anyone have thoughts on this? Do you think this is going to be detrimental to my med school education and future career in any way? I did fine in all my math classes, but I've always been petrified of speed math, and it seems like in the "real world" i.e. work/shopping/tipping, most people just rely on mental math skills.

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[QofQuimica]

Kinda off-topic, but I was calculating housing costs today and was reminded of how much I suck at mental math. Here's my question:

When you multiply/add/divide in your head, do you have trouble holding all the numbers in your head? Because I do--it requires so much concentration on my part, and I'm soooo slow, not to mention frequently inaccurate because I forget the numbers I was initially multiplying/dividing. I've wondered if it's something that gets better the more you do it, or if some people (like me!) just don't have enough working memory to do mental math quickly!

Anyone have thoughts on this? Do you think this is going to be detrimental to my med school education and future career in any way? I did fine in all my math classes, but I've always been petrified of speed math, and it seems like in the "real world" i.e. work/shopping/tipping, most people just rely on mental math skills.

One thing I do sometimes when I teach prep courses (like MCAT) where no calculators are allowed is to race my students where they use calculators to solve problems and I solve them without one. I have to do this because otherwise they don't believe me that using calculators actually slows you down. They are amazed that I can do the calculations faster in my head than they can do them using the calculator. It's not because I'm some kind of math genius. It's because I have learned tricks to do math quickly in my head. The good news is that anyone can learn these tricks; you can even buy books that teach you how to do them. Good math skills WILL help you on the MCAT and other standardized exams. Plus, it's useful to be able to do things like calculate a 15% tip quickly without a calculator when you go out to eat. 🙂

 

[oxeye]

Plus, it's useful to be able to do things like calculate a 15% tip quickly without a calculator when you go out to eat. 🙂

LOL, I guess you can't do this everywhere, but where I live sales tax is 7.375%. When I go out to eat, I just double the tax and it's around 15% of the bill. 😉

For the original poster - I love my calculator, and I majored in statistics as an undergrad. ;-) I can do calculations in my head, but it's definitely slower for me and less accurate than my wonderful calculator. I do think you can get good at it if you do it a lot. I've improved a lot with it since hiding my calculator after I learned they weren't allowed on the MCAT.

 

[QofQuimica]

LOL, I guess you can't do this everywhere, but where I live sales tax is 7.375%. When I go out to eat, I just double the tax and it's around 15% of the bill. 😉

Really? Your sales tax is fractional? Any reason in particular, or they just don't like full percents where you live? 😉

I think that a lot of people cheat and just pay 20% tip. 😛

 

[sweetstuff25]

Really? Your sales tax is fractional? Any reason in particular, or they just don't like full percents where you live? 😉

I think that a lot of people cheat and just pay 20% tip. 😛

how do u calculate 15% sales tax quickly anyway? only when an item costs multiples of 100 bux it's easy.

 

[MediMama23]

how do u calculate 15% sales tax quickly anyway? only when an item costs multiples of 100 bux it's easy.

Move the decimal place to the left one (that's 10%), then divide that number by 2 (that's 5%), and add. Q, do you have another method?

I'm also from a state where you can multiply the sales tax and roughly come up with the tip. 👍

 

[sweetstuff25]

Move the decimal place to the left one (that's 10%), then divide that number by 2 (that's 5%), and add. Q, do you have another method?

I'm also from a state where you can multiply the sales tax and roughly come up with the tip. 👍

sweet thx!

 

[HunterGatherer]

EK has some nice math tricks in their complete package and in their audio osmosis. Start practicing without a calculator and train your brain to work more efficiently. This is something that CAN be learned.

 

[NonTradMed]

In China, mental math is part of the standard math curriculum. It doesn't take a genius to learn it, only tons of practice. I had to do everything without a calculator until high school, even though I spent all my academic career in the US and I was very fast with mental arithmatic. Of course, as soon as I stopped mental math, my skills atropied to the point I can't do simple multiplication without pausing for a bit.

For the MCAT, I highly recommend sharpening your mental math skills. It's all about speed on the MCAT, and knowing how to think quick on math problems will save you critical time.

 

[QofQuimica]

Move the decimal place to the left one (that's 10%), then divide that number by 2 (that's 5%), and add. Q, do you have another method?

Nope, that's what I do, too. With a little bit of practice, you can calculate the tip before person B can even punch the numbers into the calculator. The brain is faster than the fingers. 😛

The sales tax method is one I've never tried, and I guess how well it works will depend not only on what your sales tax is, but also on whether everything you buy gets taxed. Not all grocery store food purchases get taxed here in FL, for example, although as far as I know restaurant meals ARE always taxed. 🙂

 

[PBandJ]

Really? Your sales tax is fractional? Any reason in particular, or they just don't like full percents where you live? 😉

I think that a lot of people cheat and just pay 20% tip. 😛

haha, i'm sure that the waitresses and waiters love it when people do that! 🙂

i always think $1 for every $6 in the bill (excluding the tax). and if the service was really good, i'll give a little more than that.

 

[oxeye]

Really? Your sales tax is fractional? Any reason in particular, or they just don't like full percents where you live? 😉

I think that a lot of people cheat and just pay 20% tip. 😛

I guess they just don't like to make the calculations as easy to do in our heads? ;-) Sales tax has always been a fraction of some percent everywhere I've lived (several counties in CA and NV).

I do the 20% tip is the service was really good - or if the waiter/waitress talked about how cute my baby is! LOL

 

[isocrazy]

I am pretty good at mental math. I have not done any hardcore in the past ... well since elementary school but I acquired it in the 2nd to 3rd grade. I do not know how easy it is for people to pick up on it if you arent good at it now.

I do most calculations in my head and i can't deny that it doesnt help.

Personally just get somebody to give u a series of questions like adding up long chains of numbers like 200 + 13 + 17 + 199 + etc etc...(mix up division multiplication addition subtraction) I think that would help.

 

[UMP]

i'm pretty good at mental math, but it's because I have this compulsion/obsession to add or multiply any series of numbers together or try to combine them to make them "happy" numbers... phone numbers license plates, etc... I honestly don't even realize when I do it anymore when I'm driving on the road. (BTW my happy numbers will generally be divisible by 5, prime, or some other pattern that I would like to repeat within the number... god I'm weird, but it helped me with my mental math 😉) (one simple tip when multiplying is to multiply by the nearest ten or five or whatever and then subtract and add.... like 26*71 would be 25*71 + 71=20*71+5*71+71= 1420 + 355 + 71 = 1846... of course this does take practice. Another favorite of mine is the good old n^2=(n-1)^2 + (2n-1) formula... which makes calculating weird squares on the mcat fairly easy like 32^2 would be 900 + 61 + 63 = 1024 ... too bad all these math shortcuts will be pretty much worthless after you get to med school 🙁

 

[funshine]

.... like 26*71 would be 25*71 + 71=20*71+5*71+71= 1420 + 355 + 71 = 1846...

😱 yeah, I've heard of that method. personally, I think it'd take me longer that way than just multiplying 26*71. Anyway, I've always had trouble holding numbers in my head when I'm doing the arithmetic. For the MCAT, I just wrote the calculations out by hand and I seemed to do OK, but I certainly envy all you human-calculators! Anyway, thanks for the suggestions. I've found that doing math problems in my head is a good way to pass time while running on the treadmill 😉 .

 

[Nutmeg]

like 26*71 would be 25*71 + 71=20*71+5*71+71= 1420 + 355 + 71 = 1846...

I do somthing close to the same, but if I get to

26*71 = 25*71 + 71

I say

25*71 = (71/4)*100 = (72/4)*100 - 25 = 1800 - 25 = 1775

then add 71. 72/4 is easy because 72 hours equals three days. I break it into days, quarters--sorts of things that you use a lot anyways. The more you use these points of reference, the easier to manipulate they get.

25 is easier to deal with than 20 and 5.

 

[ND2005]

I'm pretty good at mental math.

Because I'm a genius.












(Disclaimer in case of standard SDN complaints: I'm joking)

 

[Tommyk7]

LOL








(Disclaimer in case of standard SDN complaints: I'm joking)[/QUOTE]