s = arc length (distance traveled by the tip of the minute hand)
r = radius of the clock
θ = measure of central angle (in radians)
in two hours, the angle swept out by the minute hand is 2/12 of a complete rotation
θ = (2/12)(2π) = π/3
s = rθ = 6(π/3) = 2π = 6.28 inches