Despite loving maths my mental arithmetic is appalling considering I'm hoping for an eventual career in trading (my flatmate who actually who graduated with a first in Maths also has this same problem but it doesn't really bother him since he wants to be an accountant anyway).
I was reading a few S&T career guides and it pretty much says the chances you'll cope in S&T if you can't do certain problems at lightning speed are minuscule.
One example.
Convert 7/16 to three decimal places then determine whether its greater than 13/32 and if so by how much in decimal terms. I have maybe a year before I really have to make a final decision about where I want to take my career so I'm hoping to improve my mental arithmetic.
Do you guys have any material you'd recommended. All the mental arithmetic books I've seen so far are aimed at 5yr olds.
To give you an idea of where I'm at now this problem took me over 30 seconds to figure out. Realistically can I improve to a competitive level or should I cut my losses and shoot for a career in IB instead (as if IB was any easier...).
practice makes perfect
Get a mental arithmetic app on your phone, a lot of free ones, and just do it when you're bored/travelling/etc and you'll get better I think.
Haha can't say I've never done that. Some of the apps are pretty good, I do it occasionally when I'm bored. Though since I've downloaded Plague Inc it's taken a back-seat... trying to decimate the world is a lot more fun.
The app I use is Math Gym, really good, costs like 2 bucks but really worth it.
I would also read Benjamins Secrets to Mental Math, that will show you how, and then its up to you to get better.
The key to getting better is focus, as in when you are walking, force yourself to square liscence plate numbers for example as you walk past them.
Also mental math isnt as crucial as its made out to be.
With mental math I always look for patterns (I know this isn't too helpful and I don't have any resources to point you at). As another poster said, practice does make perfect. The problem you gave as an example is again about patterns and knowing just a few quick fraction -> decimal conversions. If an interviewer expects you to solve a problem quickly then there must be a trick (similar to GMAT problems, they are never overly complicated).
For your example.
7/16 is 1/16 less than 0.5. I usually know 1/1 - 1/20 in my head, but even if you just know up to 1/10 you are fine. Since 1/8 = 0.125 then 1/16 is 0.0625. So 0.4375.
Next we immediately know that 7/16 is greater than 13/32 because 7/16 is 14/32 so that is easy. Now to say how much in decimal places, look at the difference, don't try to convert 13/32 to decimals and subtract.
The difference is 1/32. The pattern I saw here (and others may see different patterns) is to convert 32 to 100, so 32* 3(1/8) which we know is 3.125. So the difference is 0.03125.
There might be easier ways to solve this, but this takes about 15 seconds.
The way I practiced these problems is simply writing down a bunch of numbers on an excel spreadsheet and multiplying 2, 3 or 4 at a time, then dividing, etc. Just over and over. Also GMAT problems are helpful since a lot of them require quick mental math tricks. Hope this helps.
http://math.usask.ca/emr/menu_arith.html http://www.buildquiz.com/speed_math.swf
Within a second you should realize 7/16 is greater than 13/32 b.c 7/16 is equal to 14/32. Now 14/32 - 13/32 = 1/32.
1/4 = .25 1/8 = .125 1/16 = .0625 1/32 = .003125
Now if you want 7/16 simply just multiple (1/16) by 7 which is equal to .4375.
Just continue to use these math tricks like whenever you multiply 88 x 23 break it down to 88 x 10 = 880 x 2 = 1760 + 88 = 1848 + 88 = 1936 + 88 = 2024
When your asked a question similar to 88 x 23 or 8^3 or the 7/16 question, whats better, to sit there for 30 seconds in silence doing the math in my head or just giving an answer thats a wrong guesstimate in about 10 seconds?
correct answer in 10 seconds
if thts not possible id go with the 30 second way but talking out loud
as in
88 x 20 = 1760 88 x 3 = 264 1760 + 264 = 2024
So just say "1760 plus 264 equals 2024" and atleast it shows you know how to do it and can think under pressure in a clear way, even though it takes a bit longer. Blurting out an answer tells them u crack under pressure.
Have you tried tradertest? I'm not allowed to post urls but I think it's a good way to start.
There are many sources on the internet, some of them are free and others not, but not much expensive at all.
Mobile/tablet apps is a great solution, you can improve your skills in your free time.
No, you won't find that kind of difficult on the tests at optiver, tibra, etc. Hard "mode" on tradertest, as you say, is crazy.
the best multiplication trick is to break it down for example 32 * 32 = (30 + 2) * (30 + 2) = 900 + 60 + 60 + 4 = 1,024. Done, you now officially look like a genius.
If you don't know the answer, try to explain the approach you would use if possible otherwise don't say you don't know only that its not my strongest skill.
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