Problem: 277 * 524
Set it up like this:
5 2 4
2
7
7
Then multiply all the intersections (normally, you don't write this step).
5 2 4
2 5*2 2*2 4*2
7 5*7 2*7 7*7
7 5*7 2*7 4*7
to get
5 2 4
2 10 4 8
7 35 14 28
7 35 14 28
Now, we'll add up the numbers diagonally, starting at the bottom right.
First diagonal:
28. Write down 8, keep the 2.
Next diagonal:
2 + 28 + 14 = 44. Write down the 4 before the 8 so we get 48, keep the other 4.
Next:
4 + 8 + 14 + 35 = 61. Write down the 1 to get 148, keep the 6.
Next:
6 + 4 + 35 = 45. Write down the 5 to get 5148, keep the 4.
Last:
4 + 10 = 14. Write it down to get 145148, which is the correct answer.
If you have decimals, just do the same thing, then count the total number of decimal digits in both numbers (for example, in 1.23 * 4.56, it would be four) and set the point so that you get that number in the result (5.6088).
Compared to what?I like this method, because it's simple and clean. First all multiplications, then all additions, and the carry comes naturally.
Imagine doing 15x35 by this method
Compared to what?
Which normally-used method does additions before the multiplications?
imaging you are in the desert and you want to calculate how much is 937 * 284 and you dont have your iphone with you...
first i will try to finish my coffee...Try to calculate 897979874 * 3948034
Thats interesting, made me go to the wikipedia page: http://en.wikipedia.org/wiki/MultiplicationThe one used in Swedish schools mixes up the operations, so it's some multiplications, then additions, then back to multiplication, then addition and so on.
I wouldnt mind keeping myself preocupied playing in the sand with numbers, till hunger gets the better of me...Also, if I'm lost in the desert, math is low on my list of priorities...
I used the 'Long Multiplication' but you were using 'Lattice Multiplication'.Thats interesting, made me go to the wikipedia page: http://en.wikipedia.org/wiki/Multiplication
You were probably using th Egpytian method!? lol or maybe modern.
I dont actually know what method i use.
I wouldnt mind keeping myself preocupied playing in the sand with numbers, till hunger gets the better of me...
Thats interesting, made me go to the wikipedia page: http://en.wikipedia.org/wiki/Multiplication
You were probably using th Egpytian method!? lol or maybe modern.
No, we are talking about doing math in lines in the sandStruggle to do any type of serious math in my head
I am from the old-school. Seldom used a calculator and, to say it all, I never "trusted" that much a calculator's answer..
Today I am an ex-teen ager (more or less) and my math abilities faded somewhat, but you won't believe how much I enjoy helping my son with his homeworks..a good excuse to listen to some AC/DC tracks while letting my writing hand fly on paper!
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