- #1
chriscarson
- 197
- 26
- Homework Statement
- Subtracting mixed numbers
- Relevant Equations
- Least common multiple
Thanks
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(Great minds think alike!)DaveC426913 said:[ DUPE ]
berkeman said:When you put the 3 fractions over the common denominator of 20, it looks like you did not convert the numerators correctly.
First step is to put the front whole number of each quantity into the numerator of each fraction without changing the denominator yet. So ##5\frac{3}{4} = \frac{?}{4}##
Then after you have converted each of the 3 quantities to pure fractions, go ahead and multiply to put them over the common denominator of 20. Does that work for you?
DaveC426913 said:[ DUPE ]
berkeman said:When you put the 3 fractions over the common denominator of 20, it looks like you did not convert the numerators correctly.
First step is to put the front whole number of each quantity into the numerator of each fraction without changing the denominator yet. So ##5\frac{3}{4} = \frac{?}{4}##
Then after you have converted each of the 3 quantities to pure fractions, go ahead and multiply to put them over the common denominator of 20. Does that work for you?
Let's start simply.chriscarson said:First step is to put the front whole number of each quantity into the numerator of each fraction ? can you tell how please ?
DaveC426913 said:Let's start simply.
For the number 1 1/2, what would that be as a fraction only? How many halves are there in and and a half?
Sorry. You're supposed to do the work, not us.chriscarson said:if you can post a picture with a written work like mine should help me better thanks
OK, how did you get that from 1 1/2?chriscarson said:3/2 ?
DaveC426913 said:OK, how did you get that from 1 1/2?
Perfect.chriscarson said:2*1+1
DaveC426913 said:Perfect.
Can you do the same for 5 3/4?
DaveC426913 said:Perfect. Now the other two in your problem.
You're going to do that next.chriscarson said:7/5 oh so my mistake was that i was making /20 ?
DaveC426913 said:You're going to do that next.
Show all your work so far.
berkeman said:Yes, now put them over the common denominator of 20, do the resulting subtraction, and you have the correct answer!
It's very, very easy to make mistakes with this kind of work, no matter how experienced you are. If you think you know how to do something but get the wrong answer, turn the page and try again. There's a fair chance you just wrote a number wrong somewhere...chriscarson said:don t ask me why but I tried this already but somehow had different answer so I gave up
well thank you all
berkeman said:Yes, now put them over the common denominator of 20, do the resulting subtraction, and you have the correct answer!
And this time you got one and minus three twentieths, right? Which is 17/20. So it looks like you actually did the maths correctly - it's just that with mixed fractions you are (by convention) not allowed to have a negative fraction. So you can write ##1\frac 12## (meaning one and a half), but ##2\frac{-1}2## (meaning two minus a half) is just something we don't write. If we get it, we either write it as ##\frac 32## or ##1\frac 12##.chriscarson said:
Ibix said:And this time you got one and minus three twentieths, right? Which is 17/20. So it looks like you actually did the maths correctly - it's just that with mixed fractions you are (by convention) not allowed to have a negative fraction. So you can write ##1\frac 12## (meaning one and a half), but ##2\frac{-1}2## (meaning two minus a half) is just something we don't write. If we get it, we either write it as ##\frac 32## or ##1\frac 12##.
Ibix said:Let's take a simple case: ##3\frac 13-1\frac 16##. Your original method would be to think ##3-1=2## and ##\frac 13-\frac 16=\frac 16## to give an answer of ##2\frac 16## - right?
Now let's try another example: ##4\frac 12-2\frac 23##. Your original method would be to think ##4-2=2## and ##\frac 12-\frac 23=-\frac 16##, to give an answer of ##2\frac{-1}6##. That's not wrong - it's just that the convention for writing numbers in this mixed form is that the fraction is always positive and less than one. This one is negative. All you need to do is work out that ##2-\frac 16=1\frac 56##.
You can have a similar problem using your methodology to add, if the fractions add up to more than one. For example ##1\frac 23+2\frac 12=3\frac 76##. But seven sixths is more than one, so you'd write ##3\frac 76## as ##4\frac 16##.
Integer you mean the whole number ?FactChecker said:Your final answer is not how you should ever write a mixed number. You can not simply concatenate the integer +1 and the fraction -3/20 directly to a proper mixed number. The integer part and the fractional part must have the same sign. Change that integer, 1, into a fraction and subtract the fraction numerators to get a valid answer.
Yeschriscarson said:Integer you mean the whole number ?
So you make 20 × 1 - 3 = 17 then / 20 .FactChecker said:Yes
To subtract fractions with different denominators, you must first find a common denominator by finding the least common multiple of the denominators. Then, convert each fraction into an equivalent fraction with the common denominator. Finally, subtract the numerators and keep the common denominator.
No, you cannot simply subtract the numerators and keep the denominators the same. This only works when the fractions have the same denominator. When the denominators are different, you must find a common denominator and convert the fractions before subtracting.
If the numerator is larger than the denominator, you have an improper fraction. In this case, you must first convert the improper fraction into a mixed number before subtracting. To do this, divide the numerator by the denominator and use the quotient as the whole number of the mixed number. Then, use the remainder as the new numerator and keep the original denominator.
Yes, it is possible to subtract more than two fractions at once. The process is the same as subtracting two fractions, but you must first find a common denominator for all the fractions involved. Then, convert each fraction into an equivalent fraction with the common denominator and subtract the numerators while keeping the common denominator.
If you end up with a negative fraction after subtracting, you can leave it as a negative fraction or convert it into a mixed number. To convert it into a mixed number, divide the numerator by the denominator and use the quotient as the whole number of the mixed number. Then, use the remainder as the new numerator and keep the original denominator.