what is the most important step to remember about multiplying a three digit factor by a one digit factor?

Question

my son is in 4th grade, it is a question for his math class

Answer 1

This question is talking about multiplying, for example, 123 x 3.

The most important step is to remember to multiply all three digits by the one digit.

So 3 x 3 = 9,    20 x 3 = 60,    and    100 x 3 = 300,    so    123 x 3 = 369.