D = r t
384 = 640 * t
384/640 = t
.6 = t .6 of an hour
.6 hr * 60min/1 hr = 36 minutes (just in case it needs to be in minutes)
The formula for the Circumference of a circle is 2•Pi•R, or 2•Radius•3.14
This is to calculate the measurements around the circle.
The formula for the Area of a circle is Pi•R^2, or 3.14•R•R
This is to calculate the entire circle.
I hope this helps!
Not sure but good luck 25•