Simple Fraction Problem: Solving Addition and Subtraction with Whole Numbers

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zak100
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Hi,
I have the following question:
2 whole number ¼ - 1 whole number 2/3 ------(1)

1 whole number (1/4 -2/3)

I am getting –ve sign which is wrong.

However if I do:

2 whole number ¼ + 1 whole number 2/3

Then:

3whole number (1/4 * 3/3 + 2/3 * 4/4)

= 3 whole number(3/12 + 8/12)

= 3 whole number 11/12

How to solve (1) in the same way as I solved the addition question.

Zulfi.
 
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zak100 said:
Hi,
I have the following question:
2 whole number ¼ - 1 whole number 2/3 ------(1)
?
What does this mean?
zak100 said:
1 whole number (1/4 -2/3)
What does this mean?
zak100 said:
I am getting –ve sign which is wrong.

However if I do:

2 whole number ¼ + 1 whole number 2/3

Then:

3whole number (1/4 * 3/3 + 2/3 * 4/4)

= 3 whole number(3/12 + 8/12)

= 3 whole number 11/12

How to solve (1) in the same way as I solved the addition question.

Zulfi.
 
I moved the thread to our homework section.

I'm making a guess: you want to calculate ##(2+\frac 1 4) - (1 + \frac 2 3 )##? Then ##(2+\frac 1 4) - (1 + \frac 2 3 ) = 1 + (\frac 1 4 - \frac 2 3)## is a valid step. The last bracket is negative, so what? Further simplification will probably include the "1+" there.
 
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mfb said:
I moved the thread to our homework section.

I'm making a guess: you want to calculate ##(2+\frac 1 4) - (1 + \frac 2 3 )##? Then ##(2+\frac 1 4) - (1 + \frac 2 3 ) = 1 + (\frac 1 4 - \frac 2 3)## is a valid step. The last bracket is negative, so what? Further simplification will probably include the "1+" there.
OKay. I got : 7/12.
Actually i forgot how i solved it which was giving negative answer. I would reply again.

Zulfi.
 
<<The last bracket is negative, so what?>>
Hi,
Thanks. Actually negative sign has significance. Its related to class 4 question. And in class 4 they learn 7-1 but not -7+1 which is -6. So negative has significance. I have to solve it in such a way that I should not get subtraction like : -7 + 1. However 7-1 is allowed. Book has that solution but at this point I don't have access to book.

Zulfi.
 
Hi,
I think its right for class 4 student. Actually they should avoid these questions. I remember studying about subtraction like 7-10 when i started studying algebra in class 6. Okay today i got that book & this is how they did to avoid subraction resulting in -ve numbers:

3⅓-1¾ = 2 + 1 +⅓-1¾=2+12/12 + 4/12 -1 whole number 9/12 = 1 whole number 7/12

Hope you would understand my text. Sorry i don't know latex. I typed it in word but can't paste here.
Actually they subtracted 3-1 which is 2. But they did not perform subtration of larger fraction 3/4 from smaller fraction 1/3 because it would result in a number with negative sign & they did not teach this in class 4.So Instead they added 1 & wrote the larger fraction with minus sign. Then later wrate 12/12 instead of 1 so that all denominators are same.
This is what i was asking.
Zulfi.
 
I think that arbitrary rule makes calculations more complicated than necessary.

Another approach would be to convert everything to x/12.

(3+1/3) - (1+3/4) = 40/12 - 21/12 = 19/12 = 1 + 7/12

(This is a readable way to write fractions without LaTeX, by the way)
 
zak100 said:
3⅓-1¾ = 2 + 1 +⅓-1¾=2+12/12 + 4/12 -1 whole number 9/12 = 1 whole number 7/12
This "whole number" business is very confusing, and was the reason your first post in this thread was so hard to comprehend. A mathematical expression should consist of numbers and operators, not words.
It would be better to write the above this way:
3⅓-1¾ = 2 + 1 +⅓-1¾=2+12/12 + 4/12 -1 - 9/12 = (2 - 1) + (16/12 - 9/12) = 1 + 7/12, or ##\frac{19}{12}##.