# Why do you have to find the least common denominator before adding or subtracting fractions?

## Why do you have to find the least common denominator before adding or subtracting fractions?

When we want to add or subtract fractions that have the same denominator, we just add or subtract the numerators, and keep the same denominator. When the denominators are unequal, we have to find a common denominator before we can add or subtract the fractions. Then we can use the LCM as our common denominator.

### Do you need a common denominator to multiply fractions?

Multiplying fractions is a lot simpler than adding or subtracting fractions because we don’t need to find a common denominator, instead we just multiply across numerators and denominators. When multiplying fractions we simply multiply the numerators together and the denominators together.

How do you subtract fractions with common 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.

Do you have to find a common denominator when subtracting fractions?

Adding Fractions: If the denominators are not the same, you must find the common denominator by finding the least common multiple (LCM). Subtracting Fractions: If the denominators are not the same, you must find the common denominator by finding the least common multiple (LCM).

## Do you need a common denominator to subtract fractions?

### What must you have to add and subtract fractions?

To add or subtract fractions they must have the same denominator (the bottom value). If the denominators are already the same then it is just a matter of either adding or subtracting the numerators (the top value). If the denominators are different then a common denominator needs to be found.

How do you add and subtract fractions with common denominators?

If the denominators are the same, then it’s pretty easy: just add or subtract the numerators , and write the result over the same denominator. You may get an answer which is not in lowest terms , even if the fractions you were adding and subtracting both were. In this case, you have to reduce the fraction .

When adding and subtracting fractions you must have?

To add or subtract fractions they must have the same denominator (the bottom value). If the denominators are already the same then it is just a matter of either adding or subtracting the numerators (the top value).