Final answer:
The length of the arc intercepted by a central angle of 4π/7 radians in a circle with radius 21 inches is (84/7)π inches.
Step-by-step explanation:
To find the length of the arc intercepted by a central angle, we can use the formula: arc length = radius * angle in radians.
In this case, the radius of the circle is 21 inches and the central angle measures 4π/7 radians.
Therefore, the arc length is: arc length = 21 inches * 4π/7.
To express the answer in terms of π, we can leave it as:
arc length = (84/7)π inches.