Jack broke apart 5x 216 as (5x 200) + ( 5× 16) to multiply mentally. what strategy did jack use?

Funny because i use the same strategy almost every time.

But as for strategy, maybe I would say distributivity, since multiplication is distributive with respect to addition.

There could have been 5, 10, or 20 students at the party.
If there were 5, each student got 4 cookies and 8 slices of pizza
If there were 10, each student got 2 cookies and 4 slices of pizza
If there were 20, each student got 1 cookie and 2 slices of pizza