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jrahhali
11-04-2005, 02:57 PM
2.8
___
5| 14
-10
---
4 0


i'm a bit confused behind the logic of this "long hand" way to division.

ok, so
5 goes into 14 2 times, so you write a 2. you then subtract the amount of times 5 can go into 14 from 14, and you get 4. Up to this point, i understand it.

why, now, do you bring down a 0, and see how many times 5 can go into 40? why does this give you your fractional part, logically?

Govtcheez
11-04-2005, 04:00 PM
Technically it's how many times it goes into 4.0, but it's a lot easier to look at it as 40 instead. The decimal point does actually come down, but we never show it because it's a lot easier to learn that way.

VirtualAce
11-04-2005, 11:55 PM
A whole number is not just the integer part that you see.

4/100 = 25

But it's 4.00... /100.00...

The zeroes are not made up, they are really there since there is 0 amount of tenths, hundreths, etc. That's why you bring the zero down because it is really there and it allows you to continue the division.

Rashakil Fol
11-05-2005, 12:37 AM
The algorithm uses this relationship:

For all values of k, x/y = k/y + (x-k)/y

For example:

To divide 84732/7, let:

84732/7 = 10000 * (8/7) + 4732/7 (We lop off all but the last
= 10000 * (1 + 1/7) + 4732/7 four digits.)
= 10000 + 10000/7 + 4732/7
= 10000 + 14732/7 (At this point, we write down '1'.)

14732/7 = 1000 * (14/7) + 732/7 (We lop off all but the last
= 1000 * (2 + 0/7) + 732/7 three digits.)
= 2000 + 0/7 + 732/7
= 2000 + 732/7 (At this point, we write down '2'.)

732/7 = 100 * (7/7) + 32/7 (We lop off all but the last
= 100 * (1 + 0/7) + 32/7 two digits.)
= 100 + 0/7 + 32/7
= 100 + 32/7 (At this point, we write down '1'.)

32/7 = 10 * (3/7) + 2/7 (We lop off all but the last
= 10 * (0 + 3/7) + 2/7 one digit.)
= 0 + 30/7 + 2/7
= 0 + 32/7 (At this point, we write down '0'.)

32/7 = 1 * (32/7) + 0/7 (We lop off all the digits.)
= 1 * (4 + 4/7) + 0/7
= 4 + 4/7 + 0/7
= 4 + 4/7 (At this point, we write down '1'.)

4/7 = 0.1 * (40/7) + 0/7 (We 'lop off' past the decimal
= 0.1 * (5 + 5/7) + 0/7 place.)
= 0.5 + 0.5/7 + 0/7
= 0.5 + 0.5/7 (We write a decimal point and a
'5'.)

0.5/7 = 0.01 * (50/7) + 0/7
= 0.01 * (7 + 1/7) + 0/7
= 0.07 + 0.01/7 + 0/7
= 0.07 + 0.01/7 (We write down a '7'.)


And so on and so forth.

Substituting expressions back up, we get the answer:

10000 + 2000 + 100 + 00 + 4 + 0.5 + 0.7 + 0.01/7
= 12104.57 + 0.01/7

VirtualAce
11-05-2005, 12:59 AM
Ok.

Our numbers are base 10. So:

12500 is

1 * (10^4)+
2 * (10^3)+
5* (10^2)+
0 *(10^1)+
0 *(10^0)

for decimals

.01 is
0 * (10^-1)+
1 * (10^-2)

I'm not sure where the other stuff from above came from, but this is why we drop zeros. If the value was not zero, you would drop that value.

white
11-05-2005, 02:00 AM
did anyone knows that there is a similar way of finding the square root of any number?
http://www.nist.gov/dads/HTML/squareRoot.html

jrahhali
11-05-2005, 11:00 AM
>>Technically it's how many times it goes into 4.0, but it's a lot easier to look at it as 40 instead.

ok. since there are 5 8's in 40, then there should 5 0.8's in 4.

gcn_zelda
11-05-2005, 05:15 PM
did anyone knows that there is a similar way of finding the square root of any number?
http://www.nist.gov/dads/HTML/squareRoot.html

I think I'll stick to local linear approximation.