shortcuts for calculations

Google "Vedic Mathematics" and you should get what you're looking for- quick calculation techniques.

rishi raj wrote:Google "Vedic Mathematics" and you should get what you're looking for- quick calculation techniques.

I checked Vedic mathematics , but that list is so big its little hard to learn all the shortcuts. is there any small list.

thanks

Hey GMATApril,

Great question - and if I can narrow it down some, I think the most important strategy for shortcutting calculations is one that I call "Look Out Below!". Look at the answer choices before you dive into a long calculation to see whether:

-An estimate or a range of numbers will suffice. If you can get away with just finding the range of the number you need (single-digit vs. teens vs. hundreds, etc.) then you may not have to do the math.

-A number property will answer it for you (for example, 432 * 333 will end in a 6...are there only 1-2 answers that do so?)

-Particularly with roots and fractions, do the answer choices give you options for what you need to factor? For example, if your last step is to reduce 124/93, the answer choices might be:

A) 5/4
B) 4/3
C) 3/2

Looking at the answers, A is out because you can't divide a 5 out of 124 or a 4 out of 93; and C is out because you can't divide a 3 out of 124 or a 2 out of 93. So B is the only possible choice - you don't need to play with 124 and 93 to figure out that they're both divisible by 31 to factor that out...you can let the answer choices guide you closer.


-Do the answer choices give you a hint as to what calculations you need to perform?

Take geometry as an example - if the answer choices include sqrt3, there's a pretty good chance that you'll use 30-60-90 triangle properties at some point...that's the most likely calculation to get you a sqrt 3. If pi is present, you're probably using the circumference or area of a circle to get that in your calculations. The answer choices that include special numbers can sometimes give you a clue...how would you likely arrive at that special number?



So my first suggestion is to practice seeing the answer choices as assets and not just as options for when you're done. They can certainly give you some important clues to make your job easier...

Thanks a lot. next time while doing such calculation i am going to use this strategy

Brian@VeritasPrep wrote:Hey GMATApril,

Great question - and if I can narrow it down some, I think the most important strategy for shortcutting calculations is one that I call "Look Out Below!". Look at the answer choices before you dive into a long calculation to see whether:

-An estimate or a range of numbers will suffice. If you can get away with just finding the range of the number you need (single-digit vs. teens vs. hundreds, etc.) then you may not have to do the math.

-A number property will answer it for you (for example, 432 * 333 will end in a 6...are there only 1-2 answers that do so?)

-Particularly with roots and fractions, do the answer choices give you options for what you need to factor? For example, if your last step is to reduce 124/93, the answer choices might be:

A) 5/4
B) 4/3
C) 3/2

Looking at the answers, A is out because you can't divide a 5 out of 124 or a 4 out of 93; and C is out because you can't divide a 3 out of 124 or a 2 out of 93. So B is the only possible choice - you don't need to play with 124 and 93 to figure out that they're both divisible by 31 to factor that out...you can let the answer choices guide you closer.


-Do the answer choices give you a hint as to what calculations you need to perform?

Take geometry as an example - if the answer choices include sqrt3, there's a pretty good chance that you'll use 30-60-90 triangle properties at some point...that's the most likely calculation to get you a sqrt 3. If pi is present, you're probably using the circumference or area of a circle to get that in your calculations. The answer choices that include special numbers can sometimes give you a clue...how would you likely arrive at that special number?



So my first suggestion is to practice seeing the answer choices as assets and not just as options for when you're done. They can certainly give you some important clues to make your job easier...