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sagiyer
Joined: 11 Jan 2012
Last visit: 30 May 2014
Posts: 7
Location: India
Concentration: Operations, Finance
Schools: ISB '15 Insead '14 NUS '15
GMAT Date: 08-31-2012
GPA: 3.7
Schools: ISB '15 Insead '14 NUS '15
Posts: 7
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Hey guys!
GMAT tests your knowledge as much as it does your ability to manage time. So, I hope this post helps you save a precious few seconds in trying to conquer the GMAT Quant section.
I believe that just by knowing how to multiply and divide by 2 (repeatedly), you can very QUICKLY handle the bigger numbers. Allow me to explain.
Multiplying by 5
say a number - 108
Now 108*5 can be written as (108/2)*10 = 54*10 = 540
338*5 = 169*10= 1690
Dividing by 5
Say a number - 162
162/5 = 162*2/10 = 324/10 = 32.4
412/5 = 824/10 = 82.4
Dividing by powers of 2, i.e 2,4,8,16,32 etc
Isnt it amazing that just by mastering dividing abd multiplying by 2 (which isnt difficult if you practice it a few times), you can do the same with much bigger numbers?
4 = 2^2 So you divide by 2, twice....say 38/4= 19/2 = 9.5
8 = 2^3 So you divide by 2, thrice....say 148/8 = 74/4 = 37/2 = 18.5
16 = 2^4, so you divide by 2, four times...548/16 = 274/8=137/4=68.5/2=34.25
the list goes on
Multiplying by powers of 2, i.e 2,4,8,16,32 etc
same goes with multiplication
4...multiply by 2 twice - 78*4= 156*2 = 312
8..112*8 = 224*4= 448*2= 896
16 = 130*16 = 260*8=520*4=1040*2=2080
Squaring any two digit number in a few seconds
Re-posting what I had posted a few minutes ago on another forum.
Here is a method to find squares of ANY 2 digit number in a matter of seconds For that you would need to remember squares of numbers upto 25, which I believe most of us know.
So, here goes:
say 44^2.
check difference with the number 25 - In this case, 44-25 = 19
Then check difference with 50 - In this case, 50-44=6. square this difference, i.e - 6^2 = 36
Now, join the 2 numbers...1936..there you go, that's your answer
A slightly more difficult number this time - Say 71
Step 1 ... 71-25 = 46
Step 2 ... 71 - 50 = 21...21 squared = 441...since we have to ensure we stick to 2 digits only, carryover the hundreds digit (4), by adding it to 46..so the result from step 1, now becomes 46+4 = 50
So, your answer is 5041
Hope the above tricks help you save those precious seconds and minutes!
GMAT tests your knowledge as much as it does your ability to manage time. So, I hope this post helps you save a precious few seconds in trying to conquer the GMAT Quant section.
I believe that just by knowing how to multiply and divide by 2 (repeatedly), you can very QUICKLY handle the bigger numbers. Allow me to explain.
Multiplying by 5
say a number - 108
Now 108*5 can be written as (108/2)*10 = 54*10 = 540
338*5 = 169*10= 1690
Dividing by 5
Say a number - 162
162/5 = 162*2/10 = 324/10 = 32.4
412/5 = 824/10 = 82.4
Dividing by powers of 2, i.e 2,4,8,16,32 etc
Isnt it amazing that just by mastering dividing abd multiplying by 2 (which isnt difficult if you practice it a few times), you can do the same with much bigger numbers?
4 = 2^2 So you divide by 2, twice....say 38/4= 19/2 = 9.5
8 = 2^3 So you divide by 2, thrice....say 148/8 = 74/4 = 37/2 = 18.5
16 = 2^4, so you divide by 2, four times...548/16 = 274/8=137/4=68.5/2=34.25
the list goes on
Multiplying by powers of 2, i.e 2,4,8,16,32 etc
same goes with multiplication
4...multiply by 2 twice - 78*4= 156*2 = 312
8..112*8 = 224*4= 448*2= 896
16 = 130*16 = 260*8=520*4=1040*2=2080
Squaring any two digit number in a few seconds
Re-posting what I had posted a few minutes ago on another forum.
Here is a method to find squares of ANY 2 digit number in a matter of seconds
For that you would need to remember squares of numbers upto 25, which I believe most of us know.So, here goes:
say 44^2.
check difference with the number 25 - In this case, 44-25 = 19
Then check difference with 50 - In this case, 50-44=6. square this difference, i.e - 6^2 = 36
Now, join the 2 numbers...1936..there you go, that's your answer
A slightly more difficult number this time - Say 71
Step 1 ... 71-25 = 46
Step 2 ... 71 - 50 = 21...21 squared = 441...since we have to ensure we stick to 2 digits only, carryover the hundreds digit (4), by adding it to 46..so the result from step 1, now becomes 46+4 = 50
So, your answer is 5041
Hope the above tricks help you save those precious seconds and minutes!
Posts: 45
Thanks sagiyer!
Some useful tips
Best
Some useful tips
Best
Thanks! Nice tips. Can you suggest more shortcut tips that can help in quick calculations?
Well you can check out some videos on Vedic maths (a very quick and efficient way of doing quick maths).
For example, Squaring a number ending in 5
let's say 65^2
The last two digits would be 5^2= 25
The first digit/digits would be= 6.7(the next number)=42
Your answer is 4225
Similarly let's square 115 (Big number...Huh!!) But it's easy.....
Last two digits: 5^2=25
First digits/digits= 11.12= 132 (Multiplication with 11 is easy: Add 012+120=132)
The answer is 13225
Hope it helps:)
For example, Squaring a number ending in 5
let's say 65^2
The last two digits would be 5^2= 25
The first digit/digits would be= 6.7(the next number)=42
Your answer is 4225
Similarly let's square 115 (Big number...Huh!!) But it's easy.....
Last two digits: 5^2=25
First digits/digits= 11.12= 132 (Multiplication with 11 is easy: Add 012+120=132)
The answer is 13225
Hope it helps:)
There are a lot of tips or tricks you could use to calculate quickly. However, please be sure to understand the concept of each tip or trick you are going to apply. It's clear that the only way to master anything is to understand it.
For multiplying or dividing with big numbers, yes it's really hard and costs too much time. For me, there are just some tricks you could use, with medium-size numbers. For example, you could calculate 125/5, 23*2, 140/4,... But how about 12.25/13, 23.78*12, 43.55*1.12,...
Remember that, in GMAT, calculation skill won't be tested but logic skill. That's it, in actual GMAT, it's better you find the best solution rather than try to remember some tricks for rapid calculation.
For multiplying or dividing with big numbers, yes it's really hard and costs too much time. For me, there are just some tricks you could use, with medium-size numbers. For example, you could calculate 125/5, 23*2, 140/4,... But how about 12.25/13, 23.78*12, 43.55*1.12,...
Remember that, in GMAT, calculation skill won't be tested but logic skill. That's it, in actual GMAT, it's better you find the best solution rather than try to remember some tricks for rapid calculation.
One tip that saves me a lot of time is to keep everything in form of fractions (half-->1/2, 20%-->1/5 etc) and then I do the appropriate simplifications and calculate the decimal if asked.
Another tip is to use appropriate letters for variables and not only x,y,z. So if the problem says Jane, Mary and Nick put j,m,n respectively so you won't be confused.
Hope these help a bit. Give a kudos if they did.
Another tip is to use appropriate letters for variables and not only x,y,z. So if the problem says Jane, Mary and Nick put j,m,n respectively so you won't be confused.
Hope these help a bit. Give a kudos if they did.
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