SOLUTION: 3/4-1/2

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Question 1143269: 3/4-1/2
Found 3 solutions by Edwin McCravy, josgarithmetic, Alan3354:
Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
On your TI-83 or TI-84,

Type this sequence of 10 key strokes:

3
/
4
-     <--[ that's the minus key -, not the negative key (-)  ]
1
/
2
MATH
ENTER
ENTER

Then read the fraction answer.

Edwin

Answer by josgarithmetic(39618) About Me  (Show Source):
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
3/4-1/2
----
For problems like this with 2 terms:
a%2Fb+-+c%2Fd+=+%28ad+-+bc%29%2Fbd
---
---> %283%2A2+-+4%2A1%29%2F%284%2A2%29+=+%286-4%29%2F8+=+2%2F8+=+1%2F4
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I remember the LCD, Least Common Denominator from grade school.
It's a waste of time.
It's not relevant to this example, but is for some other problems.
-----
For example:
3%2F4+%2B+1%2F3+%2B+5%2F6
The LCD is 12, but there's no good reason to waste time finding it.
Use the product of the 3 DENs': 4*3*6 = 72
--> 54%2F72+%2B+24%2F72+%2B+60%2F72+=+138%2F72
Then reduce.
= 23%2F12
-----------
Another example:
4%2Fa+%2B+b%2Fc+%2B+5%2Fac
Use the product: a%2Ac%2Aac+=+a%5E2c%5E2
---> %284ac%5E2+%2B+b%2Aa%5E2c+%2B+5ac%29%2Fa%5E2c%5E2
= %284ac%5E2+%2B+a%5E2bc+%2B+5ac%29%2Fa%5E2c%5E2
= %284ac+%2B+a%5E2b+%2B+5a%29%2Fa%5E2c
= %284c+%2B+ab+%2B+5%29%2Fac
=================
Using the product and reducing the result takes less time than finding the LCD in most cases.
IDK why schools and texts persist with the LCD.