# What is the Least Common Multiple of 5 and 9?

*Least common multiple* or lowest common denominator (lcd) can be calculated in two way; with the LCM formula calculation of greatest common factor (GCF), or multiplying the prime factors with the highest exponent factor.

Least common multiple (LCM) of 5 and 9 is **45**.

LCM(5,9) = 45

## Least Common Multiple of 5 and 9 with GCF Formula

The formula of **LCM** is LCM(a,b) = ( a × b) / GCF(a,b).

We need to calculate greatest common factor 5 and 9, than apply into the LCM equation.

GCF(5,9) = 1

LCM(5,9) = ( 5 × 9) / 1

LCM(5,9) = 45 / 1

LCM(5,9) = 45

## Least Common Multiple (LCM) of 5 and 9 with Primes

Least common multiple can be found by multiplying the highest exponent prime factors of 5 and 9. First we will calculate the **prime factors of 5 and 9**.

### Prime Factorization of 5

Prime factors of 5 are 5. Prime factorization of **5** in exponential form is:

5 = 5^{1}

### Prime Factorization of 9

Prime factors of 9 are 3. Prime factorization of **9** in exponential form is:

9 = 3^{2}

Now multiplying the highest exponent prime factors to calculate the **LCM of 5 and 9**.

LCM(5,9) = 5^{1} × 3^{2}

LCM(5,9) = 45