The diameter of one bicycle wheel is 28 inches and its spokes run from the hub (or center) to the edge of the rim. The diameter of another bicycle wheel is 21 inches. What is the difference in inches between the length of the spokes of the two wheels?
The spoke is equivalent to the radius which is the diameter / 2
Therefore, the spoke for the 28-inch wheel is 14 inches.
The spoke for the 21-inch wheel is 10.5 Inches.
14 - 10.5 = 3.5-inch difference between spokes.