home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
The Human Calculator
/
The Human Calculator.bin
/
hc
/
sub.txt
< prev
next >
Wrap
Text File
|
1993-08-13
|
1KB
|
63 lines
*Subtraction is really reverse
addition. When someone asks you,
"What is 14 minus 8 ?", don't
think, "14 take away 8 is what?".
Instead, ask yourself, "What
added to 8 equals 14 ?".$
The answer is 6. Visualize it like
this: (Think, 6 + 8 = 14) $
This method works on bigger numbers
too. Try it on 299 minus 151.$
Work from left to right. Think,
"100 plus what equals 200?"
The answer is 100; it becomes the
base number.$
Go to the next column:
50 plus what equals 90?
The answer is 40. Add this to your
base number. 100 + 40 = 140.$
Go to the next column:
1 plus what equals 9?
The answer is 8. So, add 8 to 140,
and you have the answer:
299 - 151 = 148$
Let's try another problem. First,
notice that the 8 in the units
column is larger than the 1 above it.
Will we have to borrow?. Let's try
doing it left to right and see.$
Begin at the left. Subtract:
70 - 30 = 40
40 is the base number.$
Go to the next column.
First, add the 1 to your base number,
then subtract 8 from that number.
71 - 38 = 33$
Let's try a 3-digit subtraction
problem. Start from the left.
600 - 200 = 400
400 is the base number.$
Now move to the right:
Add the 30 to the base number,
then subtract 50 from that total.
Now the base number is 380.$
Move to the right:
Add the 7 to the base number. The
new base number is 387. Subtract
the 5.
387 - 5 = 382
So: 637 - 255 = 382@