helicopter rotor has four blades

[Whatupdoc]

A model of a helicopter rotor has four blades, each of length 3.90m from the central shaft to the blade tip. The model is rotated in a wind tunnel at a rotational speed of 480rev/min .

A.) What is the linear speed of the blade tip?

given
R= 3.9
T = 480

would it just be V= 2*pi*R/t
and got = .05105

someone helped me(not at this forum) and the answer is wrong. can someone help? isnt it just asking for the velocity?

[K.J.Healey]

Well you say the rotational velocity is 480 rotations / minute
1 rotation at a distance R from the center is the cirumference of a circle, so the distance the tip travels in one rotation is : 2*Pi*Radius meters

D = 2*3.14159*3.90 = 24.5 meters

You say 480 Rot/Min => 480 (rotrotations/minute) * (24.5 meters/rotation) = 11760 meters per minute.