What is double stroking​

The double stroke roll works just like the single stroke roll - it's played in a sequence of alternating strokes (roll). But instead of having one stroke per hand you'll have two, as shown on the sheet music below. You can use full wrist turns to play each stroke of the double stroke at slower speeds.

Explanation: hope this helps!

Explanation:

it is played as a sequence of alternating strokes

i think it's 35 meters

e/c, where e is its total energy