Answer:
7/10 pi (radians)
Explanation:
The formula for sector area is (angle * r^2)/2
140pi = angle*r^2/2
multiply both sides by 2
280pi = angle * r^2
r = 20 cm (substitute)
280pi = angle * (20)^2
280pi = angle * 400
Divide both sides by 400
7/10 pi = angle