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simplifying multiplication with large numbers
When given a multiplication problem with large numbers, what is the best way to try to simplify. For example in a rates problem, if you are given that a person runs at 14.5 miles per second and you are trying to find how fast they run in miles per hour, what it the best way to solve this in the shortest amount of time?
- Aragorn
Re: simplifying multiplication with large numbers
guest Wrote:When given a multiplication problem with large numbers, what is the best way to try to simplify. For example in a rates problem, if you are given that a person runs at 14.5 miles per second and you are trying to find how fast they run in miles per hour, what it the best way to solve this in the shortest amount of time?
I use a mind trick to know if to divide or multiply. If 14.5m in 1 second, definitely more in 1 hr...so multiply 14.5x60x60. Since I don't know the multiplication table of 36, I will multiply separately by 60, then by 60 again.
Btw, a trick question...if some person is running 14.5 miles per second, what is his name?
Answer (highlight to reveal) : Sonic the hedgehog :lol:
- StaceyKoprince
- ManhattanGMAT Staff
- Posts: 9355
- Joined: Wed Oct 19, 2005 9:05 am
- Location: Montreal
Funny, Aragorn. :)
The first thing you should do is check the answer choices. Usually when you have to do annoying calculations, you can actually estimate.
I do the same thing Aragorn does: set up the conversion (in this case 14.5 * 60 * 60) and then just see what the easiest way is to estimate. 14.5 is about 15. So I could do 60*60 = 3600. Multiple that by 10 to get 36,000. Take half of that (which is equal to 3600 * 5) = 18,000. Add them up. (10+5=15) 36k + 18k = 54k. And for these kinds of calculations, that should be more than close enough on this test.
A little tip: you shouldn't start ANY math problem without first looking at the answer choices. The format and spread of the answers often gives you very important clues about how to approach the problem. That also means that, when you study, you need to add this to your list of study questions: how do I learn how to make the answer choices work for me? What do various characteristics usually signify? eg, a wide spread in the answers signifies I can estimate!
The first thing you should do is check the answer choices. Usually when you have to do annoying calculations, you can actually estimate.
I do the same thing Aragorn does: set up the conversion (in this case 14.5 * 60 * 60) and then just see what the easiest way is to estimate. 14.5 is about 15. So I could do 60*60 = 3600. Multiple that by 10 to get 36,000. Take half of that (which is equal to 3600 * 5) = 18,000. Add them up. (10+5=15) 36k + 18k = 54k. And for these kinds of calculations, that should be more than close enough on this test.
A little tip: you shouldn't start ANY math problem without first looking at the answer choices. The format and spread of the answers often gives you very important clues about how to approach the problem. That also means that, when you study, you need to add this to your list of study questions: how do I learn how to make the answer choices work for me? What do various characteristics usually signify? eg, a wide spread in the answers signifies I can estimate!
Stacey Koprince
Instructor
Director, Content & Curriculum
ManhattanPrep
Instructor
Director, Content & Curriculum
ManhattanPrep
3 posts Page 1 of 1