A scene from “Elementary, My Dear”

Two times ten is twenty, eleven twice is twenty-two,

Double twelve that's twenty-four, thirteen twice is twenty-six,

Fourteen twice is twenty-eight, fifteen twice is thirty, now you're buildin' up on thirty:

Sixteen twice is thirty-two, elementary.

Seventeen twice is thirty-four, elementary.

Eighteen twice is thirty-six, elementary.

Nineteen twice is thirty-eight, elementary.

Twenty twice is forty, and it must occur to you,

You can double any number, all you do is multiply by two...