Answer
$20$
Work Step by Step
The least common multiple ($LCM$) of two numbers $a$ and $b$ is the smallest number which is a multiple of both numbers $a$ and $b$..
We have to determine the $LCM$ of the numbers $4$ and $5$.
First we write the prime factorization of each number:
$4=2\cdot 2$
$5=5$
Then we take each factor the greatest number of times that it appears in any one prime factorization:
$LCM=2\cdot 2\cdot 5 = 20$.
The $LCM$ of the given numbers is $20$.
