Hello Fellow Aspirants,
This is my very first thread on GMAT Club, so if there are any mistakes or if any improvements can be made in the content then please comment below.
I am a maths enthusiast and I like to learn various methods to increase my calculation speed without depending on the calculator. I used to study Vedic mathematics in my high school and remember quiet a few techniques that I will be happy to share here.
Note: If such a thread is irrelevant/doesn't add anything useful to the community, then admin please let me know so that I can take this thread off ASAP.
My aim:I wanted to make a thread where I could keep all the formulae, concepts and tricks at one place, so that I don't have to go through the various sources again and again. I want to share the same with the community.
1. How to find square root of a number
Example: Find the square root of 28376.
Step 1: Start by making pair of digits from the right until only 1 or no digit is left at the extreme left.
Our example would look like --> 2 83 76
Step 2: Find the number whose square is less than or equal to the extreme left one remaining digit or the pair of digit.
In our example since we have only 2 as the extreme left digit, we will search for a number whose square is less than or equal to 2. Clearly it's 1.
So, we have 1 (divisor) *1 (quotient)=1. Subtract 1 from 2. The remainder is 1. Now carry the next pair of digits, 83, besides 1 (just as you do in long division method).
We have quotient as 1 for now.
Step 3: Now add quotient to divisor. We get 1+1=2. Now think of a units digit D such that 2D*D<=183.
D=6 because 26(divisor)*6(quotient)=156<183 and 27*7=189>183.
Now subtract 156 from 183. We get remainder 27.
So now the quotient is 16.
Again carry the next pair of digits besides 27.
Step 4: Add 6(previous quotient) to 26(previous divisor). We get 32. The dividend this time is 2776.
Think of a digit D such that 32D*D<=dividend.
Clearly D=8; 328*8=2624<2776 and 329*9=2961>2776. Now subtract 2624 from 2776. We get 152.
Quotient = 168
Step 5: Now bring a pair of zeros besides the previous dividend such that a decimal comes into picture.
So dividend=15200
divisor=328(previous divisor)+8(previous quotient)=336
Again think of digit D such that 336D*D<=15200.
Clearly D=4; 3364*4=13456<15200 and 3365*5=16825>15200. Now subtract 13456 from 15200. We get 1744.
The quotient = 168.4
Thus continuing with this strategy you get quotient= 168.4517; The result can be verified via calculator!
The process might be looking tedious but it is simple long division which takes 10 -15 seconds max to find the desired value.2. Find square of a number with units digit as 5
Example: \(75^2\)
Step 1: 5*5=25
Step 2: 7(tenth digit)*8(tenth digit+1)=56
Thus, \(75^2\)=5625; Result can be verified via calculator!
Hope the thread helps people is some way or the other.*This is an ongoing thread in which I will add different variety of material including formulae/tricks/concepts*