Thread: Not getting the subtraction part neither

1. Not getting the subtraction part neither

Subtract: ${5}\frac{{1}}{{8}}-{4}\frac{{7}}{{8}}$

Box 1: Enter your answer as a reduced mixed number or as a whole number. Example: 2 1/2 = 2 1/2, or 2_1/2 = 2 1/2
Enter DNE for Does Not Exist, oo for Infinity

^.. Walk me through the steps please.

2. Re: Not getting the subtraction part neither

There are many ways to do this, but the systematic way to to get common demoninators everywhere. In this case, that means converting the mixed fractions into simple fractions - each with demoninator 8. Then combine them (subtract them). Then, if necessary, write the result as a reduced mixed number (do the division and write the remainder in fraction form).

I'll do one step to get you started:

$5 \frac{1}{8} = 5 + \frac{1}{8} = \frac{5}{1} + \frac{1}{8} = \frac{(5)(8)}{(1)(8)} + \frac{1}{8} = \frac{40}{8} + \frac{1}{8} = \frac{40 + 1}{8} = \frac{41}{8}$

Now do the same thing for $4 \frac{7}{8}$, and then you'll be ready to subtract them.

3. Re: Not getting the subtraction part neither

4 7/8 = 4 + 7/8 = (4)(8)= (7)(8) +7/8 = 32/8 +7/8=32+8/8=40/8

5?

4. Re: Not getting the subtraction part neither

Another way to do it is this:

(First, suppose the problem were 51- 47. Since 7 is larger than 1, you have to "borrow" from the tens place: 11- 7 is 4 and since we have borrowed from the tens place, similarly, we have 4- 4= 0 so 51- 47= 04= 4.)

To subtract $5\frac{1}{8}- 4\frac{7}{8}$ note that you cannot subtract 7 from 8 we have to "borrow" from the ones place: $1+ \frac{1}{8}= \frac{8}{8}+ \frac{1}{8}= \frac{9}{8}$ and $\frac{9}{8}- \frac{7}{8}= \frac{2}{8}= \frac{2}{2(4)}= \frac{1}{4}$. And since we have borrowed from the 5 we have 4- 4= 0. $5\frac{1}{8}- 4\frac{7}{8}= \frac{1}{4}$.

5. Re: Not getting the subtraction part neither

Originally Posted by Rosestar
4 7/8 = 4 + 7/8
Yes, that's true.

= (4)(8)= (7)(8) +7/8
What? how did this happen? You are writing "=" between things that are not equal! Don't do that!
= 32/8 +7/8
Now you are back on the right track

=32+8/8=40/8
It would be better to use parentheses: (32+ 8)/8= 40/8. But now "7" suddenly became "8". How did that happen?

5?

6. Re: Not getting the subtraction part neither

Originally Posted by Rosestar
Subtract: ${5}\frac{{1}}{{8}}-{4}\frac{{7}}{{8}}$
This is a pure and simple rant.
The mathematics education community should 'outlaw' mixed fractions.
That community pushes calculators and/or computer algebra systems neither of which handles those. I do not understand how you have both ways. It has to be the force of habit.