Fractions!
Problem
=======
ok the problem has changed to an entirely diffrent kind of beast
i am having problems with basic math principles i guess
the problem i had in the previous question was when u have to divide 2
by 1 and 3/4 i was ariving at the answer of 1 and 8/3 witch was rong
i took the problem and devided 2 by 1 and 3/4 in the comp calculator
and got 1.375 witch comes out to 1 and 3/8 i dont know what i did rong
in my equation compared to the calculators answer
i dont need to know how to solve the geometry problem nemore i need to
figure out how to sovle the problem with in it
Problem
=======
Well, I dunno about this "calculator" stuff :-)
answer = divide 2 by 1-3/4
= 2 / 1-3/4
= 2 / 7/4
= 2 * 4/7
= 8/7
= 1-1/7 ("one and one seventh")
To do that, I used two very handy things that have stuck with me since
high school - they're even handy when designing spacecraft orbits,
calculating airflow over wings, and fixing a triple batch of pancakes
that calls for 1-1/4 cups of some messy crap.
First handy thing
=================
Convert 2-3/4 to a single fraction in the form x/y
First, imagine a picture of it:
3
2 -
4
Take the 4 and slide it up over to the 2, and multiply them: 4 * 2
is 8.
Then take that answer, 8, and slide it up over to the three and add
them: 8 + 3 = 11.
Now we've slid the numbers around till we have one number, 11, over the
other number, 4. The answer is
11
--
4
Second handy thing
==================
Say you have to divide 2 by 3/4. @!#$
2 / 3/4 is THE VERY SAME THING as 2 * 4/3
When you're dividing by a funky fraction, multiply by its reciprocal
because that's 10000 times easier. What's the reciprocal of 3/4?
It's 4/3.
And to find 2 * 4/3,
4
2 * -
3
Slide the 2 up over to the 4 and multiply them, which gives you 8.
There, you have one number over the other:
8
-
3
Third handy thing
=================
Yeah, I said there were two. Here's the script I run through to do
this. It takes about half a second to DO, but it takes at least 119
words to EXPLAIN.
Reduce 8/3 to "x and mumble thirds".
Start with the 3. 3 times 1 is 3. That's less than 8, so try the
next one. 3 times 2 is 6. That's less than 8, so try the next one.
3 times 3 is 9. Too far. Back to 3 times 2. TWO. That's the x in
"x and mumble thirds". Remember it and continue by saying the phrase
"TWO and ..."
3 times 2 is 6. 8 - 6 is 2. TWO. Continue your phrase "... TWO ..."
Then look at the number on the bottom: THREE. Finish your phrase
"... THIRDS".
So when you're done you've said "Two and two thirds", which happens to
be the right answer.
Author: Bill White <minutiae@gmail.com>
Date: 2009-09-12 18:28:30 CDT
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