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Lesson 5: Adding and subtracting fractions with unlike denominators word problems

# Add and subtract fractions: FAQ

## How do we estimate fractions to add or subtract them?

One way to estimate fractions is to round them to the nearest half or whole number. For example, $\frac{2}{3}$ rounds to $\frac{1}{2}$, and $\frac{7}{8}$ rounds to $1$.
Try it yourself with this exercise:

## How do you add and subtraction fractions visually?

To add or subtract fractions, they need to have the same denominator. We can use fraction bars to visually compare the fractions so we can add and subtract.
Try it yourself with this exercise:

## What's the difference between adding and subtracting fractions with like denominators and adding and subtracting fractions with unlike denominators?

When the denominators are the same, we can add or subtract the numerators directly. When the denominators are different, we need to find a common denominator first.
Try it yourself with these exercises:

## How do we find common denominators?

There are a few different ways to find common denominators. One way is to use the least common multiple (LCM) of the two denominators. Another way is to just multiply the two denominators together.
Try it yourself with these exercises:

## What are mixed numbers and how do we add and subtract them?

Mixed numbers are numbers that contain both a whole number and a fraction. For example, $2\frac{1}{2}$ is a mixed number. To add and subtract them, we have to find a common denominator. Then, we rewrite the mixed numbers as improper fractions with that denominator. Lastly, we add or subtract the two improper fractions together and simplify the result if needed.
Try it yourself with these exercises:

## Want to join the conversation?

• how to regroup mixed numbers and what is regrouping?
• you regroup a mixed number by taking 1 away from a number like three and add it to the fraction which is 1/8 by having the numerator and denominator for the 1 to be the same and add the 1/8. you just regrouped a mixed number! Also, regrouping is when you take 1 or mor away from a place value and add it to a lower place value to subtract. for addition, you take the extra 1 or more from a recent place value to a higher place value to add.
• what is lcm
• It's the Least Common Multiple. It's like the smallest multiple that two or more numbers have in common.
• How are you supposed to solve a fraction problem where you are taking away a smaller number from a bigger one. Take this example.
1/2-2/5
You cannot take 2 away from 1 without getting a negative number, but 2/5 is smaller then 1/2, so how do you solve the problem.
• the answer is 1/10 and thats because of:

first you take the LCM of 2/5 and 1/2 equaling 10

As you can see that the dominators are the same so you multiply the top one [ numerators ] like you did to the bottom.

If you didn't understand this whole explanation, watch the khan videos again and again so, u can understand this.

okay bye.
(1 vote)
• how do you regroup t improper fractions
• what is LCM ?
• LCM is when you try to make two different denominator into same denominator. For example: What is 2/3 + 2/4? then the answer will equal to 6/12 + 8/12. Answer=14/12.
• Thank you so much for this! It helped a lot! But my only question is does this require LCD?
• So, if mixed numbers are numbers that contain both a whole number and a fraction, how do we multiply and divide them? After this question, try experimenting with different numbers and find the least common denominator to those numbers.
• what is the highest number
• There is no highest number, because numbers can go forever.