Optiver/Tibra vs BB Mental Maths test
Was just wondering if someone could shed some light on this. For BB's you hardly get tested on your mental math, maybe a couple 49x49 or 78x62 but thats it.
Whereas for Optiver or Tibra they make you take one of those 80 questions in 8 minutes test with a high passing mark.
The thing is, Optiver and Tibra are also market makers so dont see why BB;s wouldnt use this test as well for trading positions.
every company has a different idea of what makes a good trader.
I just want to share a useful trick.
For 49 X 49:
a^2- b^2 = (a+b)(a-b)
a^2 = (a+b)(a-b)+b^2
Let b =1
49^2=(48)(50)+1^2 = 2400+1=2401
The trick works very well for squaring any number. You just need to find the right b so you can multiply easy numbers.
In this case its quite simple to just do (50-1)^2=2500+1-100
Useful trick my ass. The easiest way to square a number is:
49 x 49 = (50 x 49) - 49.
99 x 99 = (100 x 99) - 99
etc etc...
You provided two examples where your method is easier, but if you have 76x76 it is much easier to go 72x80+16 = 5776
aka whatever b gets zero in a ones column.
nice trick, and yes every bank will look for soemthing different
e.g. 7676. you take one of the 76 and set it to 80, the other to 72. i.e. set one to end as zero, and subtract the added amount from the other number. multiply them, and add the square of amount changed i.e. 4^2. so it would be 8072+16
why not just do (x-4)^2 and set x=80 --> we have x^2 -8x + 16 or 80^2-8*80 +16
It's funny, all my BB Interviews didn't have any actual math, more prob/stats/brain teasers. The only mental math question I got was the sum of 1 to 10:
Sum n(i) = n(i) *n(i+1)/2
no way to do that for big numbers other than with that equation, you'll be there for days
If you have to use systems such as Trachtenberg's do you actually have the math skills to succeed as a trader? Are these mental math tests just for screening large numbers of applicants or does trading demand daily mental math like 29^2?
OP, sorry this has turned into how best to do mental maths sorry i'm about to contribute to this
(a+b)^2 = ... is not a great method for mental calc imo
you have to remember two numbers
a^2
b^2
make another calculation
2ab
then add 3 numbers together
there are other ways of - multiplying numbers around 50; and - squaring numbers
i won't explain them here, 'cos it'll sound more complicated than (a+b)^2 = ... and people will say 'that's not easier you stupid...'
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