#### Answer

least; smallest

#### Work Step by Step

1. Step: List the Multiples of each number.
The multiples of $3$ are $3, 6, 9, 12, 15, 18, \dots$ etc
The multiples of $5$ are $5, 10, 15, 20, 25,\dots$ etc
2. Step: Find the first Common value.
The Least Common Multiple of $3$ and $5$ is $15$.