Today we’re going to find out why, when we’re adding and subtracting fractions, **they need to have the same denominator**. If you didn’t already know, when we’re adding and subtracting fractions, they must be homogeneous.

## How do you add fractions when the denominators are the same?

To make the denominators the same we can: **Multiply top and bottom of each fraction by the denominator of the other**. We simplified the fraction 2032 to 1016 , then to 58 by dividing the top and bottom by 2 each time, and that is as simple as it can get!

## What is the least common denominator of 7/10 and 3 5?

Calculate the LCM

The least common multiple of 3, 5, 7 and 10 is **210**.

### Why do you not add denominators?

When adding fractions, why don’t you add the denominators? **A denominator indicates how many equal pieces make one unit**. If you add the denominators when adding fractions, the new denominator won’t describe how many equal pieces are in one unit.

### Can you cancel out when adding fractions?

**Cross-cancellation** is really a special version of simplifying fractions. You can only take advantage of it when multiplying or dividing fractions. … You get the same answer if you multiply first, and then simplify, but it can be a lot more work. Cross-cancellation is just a shortcut, but a good one.

### What are the four rules of fractions?

- Rules for fractions. tudent.
- C. earning.
- L. S. …
- ADDITION AND SUBTRACTION. To add or subtract fractions they must have the same denominator (the bottom value). …
- Addition and Subtraction with different denominators. If the denominators are different then a common denominator needs to be found. …
- MULTIPLICATION. …
- a. …
- DIVISION.

### What if there is no denominator?

If the denominator of a fraction is zero, the expression is not a legal fraction because it’s overall value is undefined. **are not legal fractions**. Their values are all undefined, and hence they have no meaning.

### What are the rules for adding fractions?

**Adding Fractions**

- Step 1: Make sure the bottom numbers (the denominators) are the same.
- Step 2: Add the top numbers (the numerators), put that answer over the denominator.
- Step 3: Simplify the fraction (if needed)

### What are the rules for multiplying fractions?

The first step when multiplying fractions **is to multiply the two numerators**. The second step is to multiply the two denominators. Finally, simplify the new fractions. The fractions can also be simplified before multiplying by factoring out common factors in the numerator and denominator.

### What are the rules for dividing fractions?

Dividing two fractions is the same as **multiplying the first fraction by the reciprocal of the second fraction**. The first step to dividing fractions is to find the reciprocal (reverse the numerator and denominator) of the second fraction. Next, multiply the two numerators. Then, multiply the two denominators.

### How do fractions cancel out?

**Cancelling fractions**

- Sometimes you can divide the top and bottom of a fraction by the same number. This is called cancelling down.
- It is also called simplifying the fraction. You often have to write a fraction in its simplest form.
- This means that you have to cancel it down until it cannot be cancelled down any more.

### When multiplying fractions can you cross cancel?

Instead of reducing the fraction at the end of the problem, we can cross-cancel before we multiply. It’s not required, but it’ll save a few steps. Cross-canceling means that when we’re multiplying fractions, **we can reduce any numerator with any denominator**.

### Why do we need a common denominator?

In order to add fractions, the fractions must have a common denominator. We need the pieces of each fraction to **be the same size to combine them together**. … These two fractions have the same denominator, so the equal parts that the whole has been split into are the same size.

### How do you solve for a common denominator?

The easiest way to find a common denominator for a pair of fractions is **to multiply the numerator and denominator of each fraction by the denominator of the other**.

### How do you subtract fractions with like denominators?

To SUBTRACT fractions with like or the same denominator, **just subtract the numerators then copy the common denominator**. Always reduce your final answer to its lowest term.

### What is the LCM of 3 and 4?

Answer: LCM of 3 and 4 is **12**.

### What is the LCM of 6 and 3?

What is the LCM of 3 and 6? The LCM of 3 and 6 is **6**.

### What is the LCD of 5 and 7?

The LCM of 5 and 7 is **35**.

### What is 3/4 divided by 2 in a fraction?

Answer: 3/4 divided by 2 in the fraction is equal to **3/8**.