Pittsburgh Arts, Regional Theatre, New Work, Producing, Copyright, Labor Unions,
New Products, Coping Skills, J-O-Bs...
Theatre industry news, University & School of Drama Announcements, plus occasional course support for
Carnegie Mellon School of Drama Faculty, Staff, Students, and Alumni.
Lifehacker: "Learn to calculate numbers quickly without a calculator with The List Universe's 10 arithmetic tricks."
8 comments:
Anonymous
said...
The number of people who say that they can no longer do multiplication or division on paper (forget about mental math) completely disturbs me. This is one great piece of evidence about how much the world has become reliant on calculators, and sometimes you need to do a calculation and by the time you've gotten your calculator, you've wasted 3 minutes of someone's day. These tips definitely can be helpful in regards to mental math, but if someone cannot even remember how to do the math on paper, then they are bound to fail when trying to do the math in their head.
I like how when we have been growing up, we have been used to using calculators. I remember when we had to do everything by hand. I never have really noticed some of these tricks they have posted...such as multiply by 11. I have always done it quickly by hand or by using a calculator, either my TI or my phone. This would be something that should be given out to kids as they are learning, it may help them in the long run.
The example they have is pretty sweet, I would say. I can do most things in my head until it gets into really large multiplication that would just be faster to grab a calculator, but squares have always been something I had to grab my calculator for, so that's a nice thing to know.
When I was younger, I was at one point in 4 math clubs, one of which was "number sense". The whole idea of the club was to have the ability to quickly do complicated mental math, often by using tricks similar to ones in the article. I still use a lot of those tricks on the fly today. They come in handy much more often then I ever thought I would need them to.
There are a lot of handy mental math things that it's good to know off the top of your head. When shopping (for calculating tax) or tipping, try to figure out what you need in terms of factors of 10% by just moving the decimal over one place. I was at a dollar store that was closing so they were having a 95% off sale, and I saw two people use cell phone calculators to figure out how much it meant everything would cost. I had to shake my head; mental math has become a thing of the past.
I feel like the problem is that people aren't forced to do math in their head. During the last two years of math, my teacher did not usually allow calculator use. This sometimes required four or five place multiplication and division. We had to do them in our head or the margins. I used to be good at mental math, but using calculator exclusively killed that early in high school. I'm lucky that my teacher forced us to re-learn it. Now I only use a calculator when I absolutely have to. A lot of these tricks sort of follow logically when you do math in your head. I never thought of the 11 trick as a trick (or the multiply by 4,5,9 etc) they just sort of have always worked.
I need some help here. I keep coming up with an answer that is wrong for the example given in this article. They say use a 2 digit number, ok I am using 25. Then take the first number (2) times it by itself (you get 4) and then add 1. So now I have 5 and then add 25 to the that.....so I get 525.....but 25 squared is 625......unless I am really screwing something up and I just can't see where.
If you need to square a 2 digit number ending in 5, you can do so very easily with this trick. Mulitply the first digit by itself + 1, and put 25 on the end. That is all!
8 comments:
The number of people who say that they can no longer do multiplication or division on paper (forget about mental math) completely disturbs me. This is one great piece of evidence about how much the world has become reliant on calculators, and sometimes you need to do a calculation and by the time you've gotten your calculator, you've wasted 3 minutes of someone's day. These tips definitely can be helpful in regards to mental math, but if someone cannot even remember how to do the math on paper, then they are bound to fail when trying to do the math in their head.
I like how when we have been growing up, we have been used to using calculators. I remember when we had to do everything by hand. I never have really noticed some of these tricks they have posted...such as multiply by 11. I have always done it quickly by hand or by using a calculator, either my TI or my phone. This would be something that should be given out to kids as they are learning, it may help them in the long run.
The example they have is pretty sweet, I would say. I can do most things in my head until it gets into really large multiplication that would just be faster to grab a calculator, but squares have always been something I had to grab my calculator for, so that's a nice thing to know.
When I was younger, I was at one point in 4 math clubs, one of which was "number sense". The whole idea of the club was to have the ability to quickly do complicated mental math, often by using tricks similar to ones in the article. I still use a lot of those tricks on the fly today. They come in handy much more often then I ever thought I would need them to.
There are a lot of handy mental math things that it's good to know off the top of your head. When shopping (for calculating tax) or tipping, try to figure out what you need in terms of factors of 10% by just moving the decimal over one place. I was at a dollar store that was closing so they were having a 95% off sale, and I saw two people use cell phone calculators to figure out how much it meant everything would cost. I had to shake my head; mental math has become a thing of the past.
I feel like the problem is that people aren't forced to do math in their head. During the last two years of math, my teacher did not usually allow calculator use. This sometimes required four or five place multiplication and division. We had to do them in our head or the margins. I used to be good at mental math, but using calculator exclusively killed that early in high school. I'm lucky that my teacher forced us to re-learn it. Now I only use a calculator when I absolutely have to. A lot of these tricks sort of follow logically when you do math in your head. I never thought of the 11 trick as a trick (or the multiply by 4,5,9 etc) they just sort of have always worked.
I need some help here. I keep coming up with an answer that is wrong for the example given in this article. They say use a 2 digit number, ok I am using 25. Then take the first number (2) times it by itself (you get 4) and then add 1. So now I have 5 and then add 25 to the that.....so I get 525.....but 25 squared is 625......unless I am really screwing something up and I just can't see where.
it's in the grammar:
If you need to square a 2 digit number ending in 5, you can do so very easily with this trick. Mulitply the first digit by itself + 1, and put 25 on the end. That is all!
252 = (2x(2+1)) & 25
2 x 3 = 6
625
Post a Comment